ci/softpipe: Re-enable GS tests that had been banned for being flaky.

Now that the flakes should be fixed, turn the coverage on.

Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8277>

.gitlab-ci.yml

@@ -1240,11 +1240,9 @@ softpipe-piglit-quick:
   variables:
     GALLIUM_DRIVER: softpipe
     # rasterpos skipped due to flakes from use-after-free of the draw vs.
-    # glsl-1.50 removed due to GS flakes
     PIGLIT_OPTIONS: >
       --process-isolation false
       -x rasterpos
-      -x glsl-1.50
       -x egl_ext_device_
       -x egl_ext_platform_device
       -x ext_timer_query@time-elapsed