Allow neutral conclusion in publishing check (flutter#4321)

It's possible for jobs to conclude in a "neutral" state; see https://github.com/flutter/plugins/runs/3534917860 for instance. Currently this causes "release" to be red when it shouldn't be.

Author: stuartmorgan-g

.github/workflows/release.yml

@@ -36,7 +36,7 @@ jobs:
         running-workflow-name: 'release'
         repo-token: ${{ secrets.GITHUB_TOKEN }}
         wait-interval: 180 # seconds
-        allowed-conclusions: success
+        allowed-conclusions: success,neutral
         # verbose:true will produce too many logs that hang github actions web UI.
         verbose: false