Fix checking for merges

Author: nicolas-grekas

.github/workflows/fabbot.yml

@@ -87,7 +87,7 @@ jobs:
         run: |
           # If a PR contains merge commits, fail the job
           gh api -H "Accept: application/vnd.github.v3+json" \
-            "/repos/$REPO_OWNER/$REPO/pulls/$PR/commits" \
+            "/repos/$REPO/pulls/$PR/commits" \
             | jq -r '.[].parents | length > 1' | grep true > /dev/null && {
               echo "::error::Merge commits are not allowed in pull requests."
               echo "Please rebase your branch."