Run cron action on ly on the tree-sitter repo (#419)

Author: eed3si9n

.github/workflows/sync.yml

@@ -7,6 +7,7 @@ on:
 jobs:
   check-and-sync:
     runs-on: ubuntu-latest
+    if: github.repository == "tree-sitter/tree-sitter-scala"
     outputs:
       all: ${{ steps.changes.outputs.all}}
       c: ${{ steps.changes.outputs.c }}