Cannot automerge if there is only one merge style

[lunny]

1. When multiple merge styles are enabled in the repository settings, the “Merge Style” dropdown appears in the pull request (PR) view, allowing users to select the “Auto Merge” option. However, if only one merge style is enabled, the dropdown does not appear, preventing the selection of “Auto Merge.”

2. Once auto merge is enabled, you can still choose auto merge from the merge style dropdown.