MAINTAINERS: Update drm/i915 bug filing URL

commit 96228b7d

 upstream.

We've moved from bugzilla to gitlab.

Cc: stable@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200212160434.6437-1-jani.nikula@intel.com
(cherry picked from commit 3a6a4f08

)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>