pcre16: drop

There's nothing that relies on this. We want to get rid of pcre and if something specifically needs to be compiled with 16-bit code unit support they can do that with pcre2 instead

pkgs/development/libraries/pcre/default.nix

@@ -14,7 +14,6 @@
 assert lib.elem variant [
   null
   "cpp"
-  "pcre16"
   "pcre32"
 ];
 

pkgs/top-level/aliases.nix

@@ -1476,6 +1476,7 @@ mapAliases {
   partition-manager = makePlasma5Throw "partitionmanager"; # Added 2024-01-08
   patchelfStable = patchelf; # Added 2024-01-25
   paup = paup-cli; # Added 2024-09-11
+  pcre16 = throw "'pcre16' has been removed because it is obsolete. Consider migrating to 'pcre2' instead."; # Added 2025-05-29
   pcsctools = pcsc-tools; # Added 2023-12-07
   pcsxr = throw "pcsxr was removed as it has been abandoned for over a decade; please use DuckStation, Mednafen, or the RetroArch PCSX ReARMed core"; # Added 2024-08-20
   pdf4tcl = tclPackages.pdf4tcl; # Added 2024-10-02

pkgs/top-level/all-packages.nix

@@ -9312,7 +9312,6 @@ with pkgs;
   };
 
   pcre = callPackage ../development/libraries/pcre { };
-  pcre16 = res.pcre.override { variant = "pcre16"; };
   # pcre32 seems unused
   pcre-cpp = res.pcre.override { variant = "cpp"; };
 

pkgs/top-level/variants.nix

@@ -119,7 +119,6 @@ self: super: {
           # causes shadowstack disablement
           pcre = super'.pcre.override { enableJit = false; };
           pcre-cpp = super'.pcre-cpp.override { enableJit = false; };
-          pcre16 = super'.pcre16.override { enableJit = false; };
         }
       )
     ] ++ overlays;