tweak approve_and_merge.yml (#71)

Author: ktr0731

.github/workflows/approve_and_merge.yml

@@ -21,5 +21,5 @@ jobs:
               owner: context.repo.owner,
               repo: context.repo.repo,
               pull_number: context.issue.number,
-              merge_method: squash
+              merge_method: "squash"
             })