chore(ci): Run prerelease.yml when it changes (#15253)

Author: ncooke3

.github/workflows/prerelease.yml

@@ -7,6 +7,8 @@ on:
   pull_request:
     # closed will be triggered when a pull request is merged. This is to keep https://github.com/firebase/SpecsTesting up to date.
     types: [closed]
+    paths:
+    - '.github/workflows/prerelease.yml'
   workflow_dispatch:
   schedule:
     # Run every day at 10pm (PDT) / 1am (EDT) - cron uses UTC times