[Leap 15.6] GTK update has conflicts in vanilla install

@as_dinnie:

As mentioned in other threads, this patch installs the SLE Gtk3 Branding – due to licensing issues …

Please notice – <Conflict with gtk3-branding-openSUSE-15.0-lp154.2.2.1.noarch>
And – Saurland’s answer here <*-branding-opensuse or *-branding-upstream>