[Style Guide] Only use the arrow for function return types if it allows you to omit redundant information
<rdar://problem/104722324>
Pull request: https://github.com/WebKit/WebKit/pull/9200
Committed 259468@main (0fa4caf58e80): <https://commits.webkit.org/259468@main> Reviewed commits have been landed. Closing PR #9200 and removing active labels.