Add geofflang as command buffer co-owner.

Geoff has nearly single-handedly developed the passthrough command
decoder and is well versed in the code in this directory.

Bug: none
Change-Id: Ic2e87bd485b4274270abbd562a729b84d3637c63
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1758737Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Victor Miura <vmiura@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688298}

gpu/command_buffer/OWNERS

 bajones@chromium.org
-zmo@chromium.org
+geofflang@chromium.org
 vmiura@chromium.org
+zmo@chromium.org
 
 # GPU memory buffer tests.
 per-file *gpu_memory_buffer*=reveman@chromium.org