Disable the sync action in forks (#19934)

.github/workflows/runtime-sync.yml

@@ -10,6 +10,8 @@ on:
 
 jobs:
   compare_repos:
+    # Comment out this line to test the scripts in a fork
+    if: github.repository == 'dotnet/aspnetcore'
     name: Compare the shared code in the AspNetCore and Runtime repos and notify if they're out of sync.
     runs-on: windows-latest
     steps: