chore: update CODEOWNERS to include admins for all (#3184)

We will soon be switching to require review from CODEOWNERS. In
order for admins to have the power to merge regen PRs with no other
reviews they need to be owners for all directories.
diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index e1f8e6f..c4b6fc3 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -1,12 +1,12 @@
 # Default owner for all directories not owned by others
 *                   @googleapis/yoshi-go-admins
-/bigtable/          @tritone
-/bigquery/          @googleapis/api-bigquery
-/datastore/         @tritone
-/firestore/         @tritone
-/pubsub/            @googleapis/api-pubsub
-/spanner/           @skuruppu
-/storage/           @tritone
-/errorreporting/    @googleapis/api-logging 
-/logging/           @googleapis/api-logging
+/bigtable/          @tritone @googleapis/yoshi-go-admins
+/bigquery/          @googleapis/api-bigquery @googleapis/yoshi-go-admins
+/datastore/         @tritone @googleapis/yoshi-go-admins
+/firestore/         @tritone @googleapis/yoshi-go-admins
+/pubsub/            @googleapis/api-pubsub @googleapis/yoshi-go-admins
+/spanner/           @skuruppu @googleapis/yoshi-go-admins
+/storage/           @tritone @googleapis/yoshi-go-admins
+/errorreporting/    @googleapis/api-logging @googleapis/yoshi-go-admins
+/logging/           @googleapis/api-logging @googleapis/yoshi-go-admins