add a changelog entry check for pull requests

.github/workflows/changelog-entry-check.yml

@@ -21,7 +21,7 @@ jobs:
     changelog-entry-check:
         uses: dbt-labs/actions/.github/workflows/changelog-existence.yml@main
         with:
-            changelog_comment: -<
+            changelog_comment: |-
                 "Thank you for your pull request!"
                 "We could not find a changelog entry for this change."
                 "For details on how to document a change, see the [dbt-postgres contributing guide](https://github.com/dbt-labs/dbt-postgres/blob/main/CONTRIBUTING.md)."