resolveConfig doc comment is out of date

[alex12058]

The doc comment for resolveConfig function is out of date. You used to be able to pass in a directory (or file) path and it would resolve any config file in that directory.

The resolveConfig function no longer works this way and expects a file path. #15910 updated the documentation for the function in docs/api.md but the doc comment on the function remains unchanged.

I will create a PR to update the doc comment.