gobject-2.0: Make FlagsClass.values weak
gobject-2.0: Make FlagsClass.values weak

In addition to 950f081bae86a98a7918b5fc4a9c3acd15681c8e

GNOME/vala,GNOME/vala,GNOME/vala,frida/vala,GNOME/vala,frida/vala,frida/vala,frida/vala,frida/vala