Do not run CI on merges to relese

PRs are merged to the release branches using our own implementation of the merge queue. The history for them is linearised and we are running all the CI both after every backported batch. Those builds are redundant and can clog our runners.

Author: Kordyjan

.github/workflows/ci.yaml

@@ -18,6 +18,7 @@ on:
       - '*'
     branches-ignore:
       - 'gh-readonly-queue/**'
+      - 'release-**'
   pull_request:
   merge_group:
   schedule: