ci: Clean up the dependencies

ci: Clean up the dependencies

The pkgconfig(gobject-introspection-1.0) dependency was added in commit
0a420404c603 ("ci: Update JS tooling") as a build-time dependency of gjs
at the time time, even though it wasn't being built from source, and the
pre-built gjs included in the image was being used.

What's needed is a C compiler to build gnome-extensions-tool, and GCC
was being pulled in by pkgconfig(gobject-introspection-1.0) through
libtool.

Related: https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2193
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3989>