.github/workflows: try to make the merge queue actually run CI

Signed-off-by: David Anderson <danderson@tailscale.com>

.github/workflows/codeql-analysis.yml

@@ -18,6 +18,7 @@ on:
     # The branches below must be a subset of the branches above
     branches: [ main ]
   merge_group:
+    branches: [ main ]
   schedule:
     - cron: '31 14 * * 5'
 

.github/workflows/test.yml

@@ -25,6 +25,8 @@ on:
     branches:
       - "*"
   merge_group:
+    branches:
+      - "main"
 
 concurrency:
   # For PRs, later CI runs preempt previous ones. e.g. a force push on a PR