nixos: remove all uses of lib.mdDoc

these changes were generated with nixq 0.0.2, by running

  nixq ">> lib.mdDoc[remove] Argument[keep]" --batchmode nixos/**.nix
  nixq ">> mdDoc[remove] Argument[keep]" --batchmode nixos/**.nix
  nixq ">> Inherit >> mdDoc[remove]" --batchmode nixos/**.nix

two mentions of the mdDoc function remain in nixos/, both of which
are inside of comments.

Since lib.mdDoc is already defined as just id, this commit is a no-op as
far as Nix (and the built manual) is concerned.

nixos/modules/virtualisation/proxmox-image.nix

@@ -10,7 +10,7 @@ with lib;
         type = types.str;
         default = "";
         example = "order=scsi0;net0";
-        description = lib.mdDoc ''
+        description = ''
           Default boot device. PVE will try all devices in its default order if this value is empty.
         '';
       };
@@ -18,7 +18,7 @@ with lib;
         type = types.str;
         default = "virtio-scsi-pci";
         example = "lsi";
-        description = lib.mdDoc ''
+        description = ''
           SCSI controller type. Must be one of the supported values given in
           <https://pve.proxmox.com/wiki/Qemu/KVM_Virtual_Machines>
         '';
@@ -27,7 +27,7 @@ with lib;
         type = types.str;
         default = "local-lvm:vm-9999-disk-0";
         example = "ceph:vm-123-disk-0";
-        description = lib.mdDoc ''
+        description = ''
           Configuration for the default virtio disk. It can be used as a cue for PVE to autodetect the target storage.
           This parameter is required by PVE even if it isn't used.
         '';
@@ -35,21 +35,21 @@ with lib;
       ostype = mkOption {
         type = types.str;
         default = "l26";
-        description = lib.mdDoc ''
+        description = ''
           Guest OS type
         '';
       };
       cores = mkOption {
         type = types.ints.positive;
         default = 1;
-        description = lib.mdDoc ''
+        description = ''
           Guest core count
         '';
       };
       memory = mkOption {
         type = types.ints.positive;
         default = 1024;
-        description = lib.mdDoc ''
+        description = ''
           Guest memory in MB
         '';
       };
@@ -65,7 +65,7 @@ with lib;
       name = mkOption {
         type = types.str;
         default = "nixos-${config.system.nixos.label}";
-        description = lib.mdDoc ''
+        description = ''
           VM name
         '';
       };
@@ -73,7 +73,7 @@ with lib;
         type = types.str;
         default = "512M";
         example = "2048M";
-        description = lib.mdDoc ''
+        description = ''
           additional disk space to be added to the image if diskSize "auto"
           is used.
         '';
@@ -82,7 +82,7 @@ with lib;
         type = types.str;
         default = "256M";
         example = "512M";
-        description = lib.mdDoc ''
+        description = ''
           Size of the boot partition. Is only used if partitionTableType is
           either "efi" or "hybrid".
         '';
@@ -91,7 +91,7 @@ with lib;
         type = types.str;
         default = "auto";
         example = "20480";
-        description = lib.mdDoc ''
+        description = ''
           The size of the disk, in megabytes.
           if "auto" size is calculated based on the contents copied to it and
           additionalSpace is taken into account.
@@ -100,7 +100,7 @@ with lib;
       net0 = mkOption {
         type = types.commas;
         default = "virtio=00:00:00:00:00:00,bridge=vmbr0,firewall=1";
-        description = lib.mdDoc ''
+        description = ''
           Configuration for the default interface. When restoring from VMA, check the
           "unique" box to ensure device mac is randomized.
         '';
@@ -109,7 +109,7 @@ with lib;
         type = types.str;
         default = "socket";
         example = "/dev/ttyS0";
-        description = lib.mdDoc ''
+        description = ''
           Create a serial device inside the VM (n is 0 to 3), and pass through a host serial device (i.e. /dev/ttyS0),
           or create a unix socket on the host side (use qm terminal to open a terminal connection).
         '';
@@ -118,7 +118,7 @@ with lib;
         type = types.bool;
         apply = x: if x then "1" else "0";
         default = true;
-        description = lib.mdDoc ''
+        description = ''
           Expect guest to have qemu agent running
         '';
       };
@@ -132,7 +132,7 @@ with lib;
           onboot = 1;
         }
       '';
-      description = lib.mdDoc ''
+      description = ''
         Additional options appended to qemu-server.conf
       '';
     };
@@ -151,7 +151,7 @@ with lib;
       type = types.str;
       default = config.proxmox.qemuConf.name;
       example = "999-nixos_template";
-      description = lib.mdDoc ''
+      description = ''
         Filename of the image will be vzdump-qemu-''${filenameSuffix}.vma.zstd.
         This will also determine the default name of the VM on restoring the VMA.
         Start this value with a number if you want the VMA to be detected as a backup of