[owners] Remove shahadath@google.com from OWNERS.graphics

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https://chromium-review.googlesource.com/q/shahadath@google.com

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Change-Id: I1236acf7a9c58bdd8698082941ae50be563a304d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/graphics/+/6122119
Reviewed-by: David Riley <davidriley@chromium.org>
Commit-Queue: David Riley <davidriley@chromium.org>
Tested-by: David Riley <davidriley@chromium.org>
Auto-Submit: Owners Cleanup <swarming-tasks@owners-cleanup-prod.google.com.iam.gserviceaccount.com>