Fix failure of new internal lint rustc::span_use_eq_ctxt

[a-lafrance]

I've implemented a new Rustc internal lint that forbids usage of .ctxt() == .ctxt() for spans, and suggests using Span::eq_ctxt directly instead (see rust-lang/rust#49509 and rust-lang/rust#116787).

Unfortunately the PR can't land yet because there's a violation of the lint in the Clippy codebase which (as it should) is causing CI failures, so this PR fixes that lint preemptively to unblock it from landing.

changelog: none

[rustbot]

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[flip1995]

You can just include those changes in your PR towards rust-lang/rust. Otherwise you'll have to wait until Thursday, when I sync this PR to the Rust repo.

r? @flip1995

So the changes LGTM, but I'm holding off with merging, as I think that it's easier for everyone if you just apply those changes in the Rust repo (src/tools/clippy)

[a-lafrance]

Ah whoops, thanks for the heads up. Didn't know I could update Clippy in-tree, that does seem much smoother.

Closing this now that I've updated the Rustc PR with the Clippy changes.

[flip1995]

Didn't know I could update Clippy in-tree,

Yes, this is encouraged for fixing up breaking changes in rustc. But functional changes like lint additions are not allowed in rustc and must be done in the Clippy repo.

[a-lafrance]

Good to know, thanks for the info :)