README: fix "Reporting bugs" section
README: fix "Reporting bugs" section

The "Reporting bugs" section gives
https://bugzilla.gnome.org/enter_bug.cgi?product=gstreamer-vaapi as the
link to report a bug, but this link says "Sorry, entering a bug into the
product gstreamer-vaapi has been disabled.".

This commit fixes the URL to point to the proper location, and also
removes the following paragraph that is no longer correct.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

https://bugzilla.gnome.org/show_bug.cgi?id=779954

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