buildLuarocksPackage: rename file to match its role

doc/languages-frameworks/lua.section.md

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 #### `buildLuarocksPackage` function {#buildluarockspackage-function}
 
-The `buildLuarocksPackage` function is implemented in `pkgs/development/interpreters/lua-5/build-lua-package.nix`
+The `buildLuarocksPackage` function is implemented in `pkgs/development/interpreters/lua-5/build-luarocks-package.nix`
 The following is an example:
 ```nix
 luaposix = buildLuarocksPackage {

pkgs/top-level/lua-packages.nix

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   buildLuaApplication = args: buildLuarocksPackage ({ namePrefix = ""; } // args);
 
-  buildLuarocksPackage = lib.makeOverridable (callPackage ../development/interpreters/lua-5/build-lua-package.nix { });
+  buildLuarocksPackage = lib.makeOverridable (callPackage ../development/interpreters/lua-5/build-luarocks-package.nix { });
 
   luaLib = callPackage ../development/lua-modules/lib.nix { };