Remove `WithKeywordsWhenNeeded`

[JonRowe]

My approach to try to split args and use **kwargs for delegation is incorrect and needs to be phased out in 3.x and this module removed in 4.x. The problem is that arguments that implement to_hash are wrongly detected (with no way to know they are not) and converted. Only ruby2_keywords delegation is safe.

See https://github.com/rspec/rspec-expectations/issues/1241 as an example of this issue.