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/services/continuous-integration/hercules-ci-agent/common.nix

@@ -36,7 +36,7 @@ in
     enable = mkOption {
       type = types.bool;
       default = false;
-      description = lib.mdDoc ''
+      description = ''
         Enable to run Hercules CI Agent as a system service.
 
         [Hercules CI](https://hercules-ci.com) is a
@@ -47,7 +47,7 @@ in
     };
     package = mkPackageOption pkgs "hercules-ci-agent" { };
     settings = mkOption {
-      description = lib.mdDoc ''
+      description = ''
         These settings are written to the `agent.toml` file.
 
         Not all settings are listed as options, can be set nonetheless.
@@ -67,7 +67,7 @@ in
       type = types.path;
       internal = true;
       defaultText = lib.literalMD "generated `hercules-ci-agent.toml`";
-      description = lib.mdDoc ''
+      description = ''
         The fully assembled config file.
       '';
     };

nixos/modules/services/continuous-integration/hercules-ci-agent/settings.nix

@@ -13,7 +13,7 @@ let
     freeformType = format.type;
     options = {
       apiBaseUrl = mkOption {
-        description = lib.mdDoc ''
+        description = ''
           API base URL that the agent will connect to.
 
           When using Hercules CI Enterprise, set this to the URL where your
@@ -25,12 +25,12 @@ let
       baseDirectory = mkOption {
         type = types.path;
         default = "/var/lib/hercules-ci-agent";
-        description = lib.mdDoc ''
+        description = ''
           State directory (secrets, work directory, etc) for agent
         '';
       };
       concurrentTasks = mkOption {
-        description = lib.mdDoc ''
+        description = ''
           Number of tasks to perform simultaneously.
 
           A task is a single derivation build, an evaluation or an effect run.
@@ -54,7 +54,7 @@ let
         '';
       };
       labels = mkOption {
-        description = lib.mdDoc ''
+        description = ''
           A key-value map of user data.
 
           This data will be available to organization members in the dashboard and API.
@@ -73,7 +73,7 @@ let
         '';
       };
       workDirectory = mkOption {
-        description = lib.mdDoc ''
+        description = ''
           The directory in which temporary subdirectories are created for task state. This includes sources for Nix evaluation.
         '';
         type = types.path;
@@ -81,7 +81,7 @@ let
         defaultText = literalExpression ''baseDirectory + "/work"'';
       };
       staticSecretsDirectory = mkOption {
-        description = lib.mdDoc ''
+        description = ''
           This is the default directory to look for statically configured secrets like `cluster-join-token.key`.
 
           See also `clusterJoinTokenPath` and `binaryCachesPath` for fine-grained configuration.
@@ -91,7 +91,7 @@ let
         defaultText = literalExpression ''baseDirectory + "/secrets"'';
       };
       clusterJoinTokenPath = mkOption {
-        description = lib.mdDoc ''
+        description = ''
           Location of the cluster-join-token.key file.
 
           You can retrieve the contents of the file when creating a new agent via
@@ -108,7 +108,7 @@ let
         defaultText = literalExpression ''staticSecretsDirectory + "/cluster-join-token.key"'';
       };
       binaryCachesPath = mkOption {
-        description = lib.mdDoc ''
+        description = ''
           Path to a JSON file containing binary cache secret keys.
 
           As these values are confidential, they should not be in the store, but
@@ -122,7 +122,7 @@ let
         defaultText = literalExpression ''staticSecretsDirectory + "/binary-caches.json"'';
       };
       secretsJsonPath = mkOption {
-        description = lib.mdDoc ''
+        description = ''
           Path to a JSON file containing secrets for effects.
 
           As these values are confidential, they should not be in the store, but