signoff for upmerge git commit (#1889)

Signed-off-by: Brooke Hamilton <[email protected]>

.github/workflows/upmerge.yaml

@@ -65,7 +65,7 @@ jobs:
           git fetch origin $SOURCE_BRANCH
           git merge --no-commit origin/$SOURCE_BRANCH
           git checkout edge -- bicepconfig.json
-          git commit -m "Upmerge to edge"
+          git commit --signoff --message "Upmerge to edge"
           
           if git diff --quiet edge; then
               echo "No changes to merge from $SOURCE_BRANCH to edge"