doc: remove reference to unix-man-urls.lua

doc/build-aux/pandoc-filters/link-unix-man-references.lua

@@ -1,6 +1,5 @@
 --[[
-Turns a manpage reference into a link, when a mapping is defined
-in the unix-man-urls.lua file.
+Turns a manpage reference into a link, when a mapping is defined below.
 ]]
 
 local man_urls = {

doc/contributing/contributing-to-documentation.chapter.md

@@ -55,7 +55,7 @@ Additionally, the following syntax extensions are currently used:
 - []{#ssec-contributing-markup-inline-roles}
   If you want to link to a man page, you can use `` {manpage}`nix.conf(5)` ``, which will turn into {manpage}`nix.conf(5)`.
 
-  The references will turn into links when a mapping exists in {file}`doc/build-aux/pandoc-filters/unix-man-urls.lua`.
+  The references will turn into links when a mapping exists in {file}`doc/build-aux/pandoc-filters/link-unix-man-references.lua`.
 
   This syntax is taken from [MyST](https://myst-parser.readthedocs.io/en/latest/syntax/syntax.html#roles-an-in-line-extension-point). Though, the feature originates from [reStructuredText](https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#role-manpage) with slightly different syntax.