mesa: remove separate enable for KHR_robust_buffer_access_behavior

This extension appears to be a strict subset of the ARB version. Also
remove it from GL3.txt since it doesn't seem relevant.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Acked-by: Jason Ekstrand <jason@jlekstrand.net>
Acked-by: Kenneth Graunke <kenneth@whitecape.org>
4 files changed