doc: Update list of dependencies.

doc: Update list of dependencies.

* gettext-tools/doc/lang-csharp.texi: Mention dotnet8 as alternative.
* gettext-tools/tests/lang-csharp: Likewise.
* gettext-tools/doc/lang-pascal.texi: Replace fpk with fpc.
* gettext-tools/tests/lang-pascal: Likewise.
* gettext-tools/doc/lang-wxwidgets.texi: Mention libwxgtk3.2-dev as alternative.
* gettext-tools/tests/lang-objc: Mention the gobjc package.
* gettext-tools/tests/lang-rst: Mention the fp-utils package.
* gettext-tools/tests/lang-vala: Mention valac as alternative.