build: do not bundle glib anymore.

We now use the GNOME 3.28 runtime and glib 2.56.0 is bundled with it.

build/flatpak/org.gimp.GIMP-nightly.json

@@ -30,35 +30,6 @@
                 "/share/glib-2.0/codegen", "/bin/gdbus-codegen", "/bin/glib-*",
                 "/bin/gobject-query", "/bin/gresource", "/bin/gtester*"],
     "modules": [
-        {
-            "name" : "glib2",
-            "config-opts" : [
-                "--with-pcre=system"
-            ],
-            "ensure-writable" : [
-                "/share/glib-2.0/codegen/*.pyc"
-            ],
-            "sources" : [
-                {
-                    "url": "https://download.gnome.org/sources/glib/2.54/glib-2.54.2.tar.xz",
-                    "sha256": "bb89e5c5aad33169a8c7f28b45671c7899c12f74caf707737f784d7102758e6c",
-                    "type": "archive"
-                }
-            ]
-        },
-        {
-            "name" : "glib-networking",
-            "config-opts" : [
-                "--disable-static"
-            ],
-            "sources" : [
-                {
-                    "url": "http://ftp.gnome.org/pub/gnome/sources/glib-networking/2.54/glib-networking-2.54.1.tar.xz",
-                    "sha256": "eaa787b653015a0de31c928e9a17eb57b4ce23c8cf6f277afaec0d685335012f",
-                    "type": "archive"
-                }
-            ]
-        },
         {
             "name": "mypaint-brushes",
             "sources": [