pluginutil: Remove Mesa from drivers white list
pluginutil: Remove Mesa from drivers white list

The Mesa Gallium driver is poorly tested currently, leading to bad user
experience for AMD users. The driver can be added back to the white list at
runtime using the GST_VAAPI_ALL_DRIVERS environment variable.

GStreamer/gstreamer-vaapi,ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi,ceyusa/gstreamer-vaapi