This reverts commit f525e1f.

This removes color control from warnings for unstable features.
For some reason this removed color support from `cargo -Zhelp` in the
tests but I can't reproduce it locally.

The most important thing was getting the config fix in.
There are two follow ups
- Can we have the config working *and* color?
- Why did this fail for this field and not the others we already had
  tests for?

I ran out my immediate time box for looking into these.

Fixes rust-lang#13991

As lint dropping_copy_types will give suggsetion in this
situation.(Changed in rust-lang/rust#125433)