build: stop auto merging releases (#1361)

Stop auto-merging releases, even if they only contain dependency updates,
as it causes a too large number of releases to go out.

Author: olavloite

.github/workflows/auto-release.yaml

@@ -99,5 +99,5 @@ jobs:
             owner: context.repo.owner,
             repo: context.repo.repo,
             issue_number: context.payload.pull_request.number,
-            labels: ['kokoro:force-run', 'automerge']
+            labels: ['kokoro:force-run']
           });