Spring Ensure removal of Content-Type header if body Publisher is empty

I added a removal of Content-Type header in org.springframework.http.codec.EncoderHttpMessageWriter if the body Publisher is empty

Added a couple of tests to assert on the writer's correct behavior when dealing with empty body Publishers

The GH-32620 issue is a blocker for a Spring Cloud Gateway issue I've been researching

Comment From: NadChel

Is there something else I need to do to have it approved and merged?

Comment From: poutsma

Thank you for submitting a PR. This will be in the upcoming 6.2M2 milestone.