[backport] borrow_deref_ref: do not trigger on &raw references

[samueltardieu]

Backport of #13600, tested in Rust beta sources.

changelog: [borrow_deref_ref]: do not trigger on &raw references

r? @xFrednet

[xFrednet]

Hey Samuel, usually backports are done all together by @flip1995 one week before the release. I usually see the changes in the Rust repo, where a PR is created into the beta branch. I know that the documentation states that the first step is to get it onto the Clippy beta branch, but I'm not sure how this is usually done.

@flip1995 Could you maybe comment on this? Also do we want to merge this or let you do the normal backport before the next release?

[samueltardieu]

I wondered about it, and I haven't seen anything in https://doc.rust-lang.org/nightly/clippy/development/infrastructure/backport.html so I wanted to try the process. I'm fine with closing this PR and letting @flip1995 merge all beta-nominated issues.

[flip1995]

The backport documentation is completely outdated. I updated the documentation in #12762, but I mixed it with the Josh move documentation. I plan to split things that are unrelated to Josh out of this and the other Josh PR.

I will include the nominated PR in the beta backport.

Merging this in the Clippy repo does nothing. The beta and stable branches are only there for documentation deployment nowadays.