Add jgruber to deoptimizer owners

Change-Id: Iba745cae7f5b90654839abefb42b21fd9c49064f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2228650
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68171}

src/deoptimizer/OWNERS

-sigurds@chromium.org
-tebbi@chromium.org
+jgruber@chromium.org
 neis@chromium.org
 nicohartmann@chromium.org
+sigurds@chromium.org
+tebbi@chromium.org
 
 # COMPONENT: Blink>JavaScript>Compiler