Revert "meson: Add schemasdir and giomoduledir to gio dependency"

This reverts commit 5aa03882.

It fails to compile on newer Meson versions with --fatal-meson-warnings due to:

WARNING: Project targeting '>= 0.52.0' but tried to use feature introduced in '0.54.0': variables arg in declare_dependency.
gio/meson.build:833:0: ERROR: Fatal warnings enabled, aborting

That happens regardless of the fact that we’ve correctly limited the use of the variables argument to only when building with Meson ≥ 0.56. Unfortunately Meson can’t statically detect that the argument is conditional.

Bumping GLib’s Meson dependency is too much work right now, so this MR unfortunately has to be reverted.