[gtksourceview] build: drop glib/gtk deps for CI

[Christian Hergert <chergert src gnome org>]

commit 2367820e5884dc0e37082b5ae95c4f8c3ab508df
Author: Christian Hergert <chergert redhat com>
Date:   Tue Sep 6 17:21:12 2022 -0700

    build: drop glib/gtk deps for CI
    
    We can compile on older releases just fine, even if it means that some
    issues would be present if that were the case.

 meson.build | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/meson.build b/meson.build
index ade8021c..ddcfb6e9 100644
--- a/meson.build
+++ b/meson.build
@@ -68,8 +68,8 @@ build_gtk_doc = get_option('gtk_doc')
 # Dependencies
 cc = meson.get_compiler('c')
 
-glib_req_version = '2.73'
-gtk_req_version = '4.7'
+glib_req_version = '2.72'
+gtk_req_version = '4.6'
 
 libm_dep = cc.find_library('m', required: false)