[turbolizer] Make sigurds@ a turbolizer OWNER

Change-Id: Ia7d37e72b16123e98b2f2e4d4e5d614f9b8c8d9e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1649558
Auto-Submit: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62053}

tools/turbolizer/OWNERS

 danno@chromium.org
+sigurds@chromium.org