OWNERS: Remove tobiast.

I never really worked here, and also won't in future.

Test: Manual code review only.
Bug: 152399425
Change-Id: I8e5faaa1a6c02eb6e52298b164aed0d77faf35f1
diff --git a/OWNERS b/OWNERS
index 90c5d36..6b17500 100644
--- a/OWNERS
+++ b/OWNERS
@@ -4,4 +4,3 @@
 jdesprez@google.com
 mrosenfeld@google.com
 siniavine@google.com
-tobiast@google.com