Long string in return annotation does not get split if there's parameters

Describe the bug This was first reported in #2699, and thought resolved in #2990, except that only solved the specific case of the function having no parameters.

To Reproduce Run the test return_annotation_brackets_string:

https://github.com/psf/black/blob/3a2d76c7bcf39e852f3b379b76537d7847ed4225/tests/data/preview/return_annotation_brackets_string.py#L1-L23

The second function should be formatted exactly the same as the first one.