- Require libgtksourceview-4-0 instead of gtksourceview4 in the
devel package: defacto the same package, as the library provides
the base name, but more explicit and clearer.
- Add libgtksourceview4 Provides to libgtksourceview-4-0 and add a
explicit Requires in devel subpackage, silence rpmlint.
- Use ldconfig_scriptlets for post(un) handling.
- Update Supplements to current standard.

We need to take a look at this:

[ 215s] glade-catalog-gtksourceview4.x86_64: W: self-obsoletion glade-catalog-gtksourceview <= 4.8.2 obsoletes glade-catalog-gtksourceview = 4.8.2
[ 215s] The package obsoletes itself. This is known to cause errors in various tools
[ 215s] and should thus be avoided, usually by using appropriately versioned Obsoletes
[ 215s] and/or Provides and avoiding unversioned ones.
[ 215s]
[ 215s] 6 packages and 0 specfiles checked; 0 errors, 1 warnings, 0 badness; has taken 1.3 s (forwarded request 929780 from iznogood)