Bump rustfix 0.8.1 -> 0.8.7
This commit can be replicated by running `cargo update -p rustfix --precise 0.8.7 && x test ui --bless`.
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The reasons this affects UI tests is as follows:
- The UI test suite runs rustc with `-Z deduplicate-diagnostics=no --error-format=json`, which means that rustc emits multiple errors containing identical suggestions. That caused the weird-looking code that had multiple `X: Copy` suggestions.
- Those suggestions are interpreted not by rustc itself, but by the `rustfix` library, maintained by cargo but published as a separate crates.io library and used by compiletest.
- Sometime between rustfix 0.8.1 and 0.8.7 (probably in rust-lang/cargo#14747, but it's hard to tell because rustfix's versioning doesn't match cargo's), rustfix got smarter and stopped applying duplicate suggestions.
Update rustfix to match cargo's behavior. Ideally, we would always share a version of rustfix between cargo and rustc (perhaps with a path dependency?), to make sure we are testing the behavior we ship. But for now, just manually update it to match.
Note that the latest version of rustfix published to crates.io is 0.9.1, not 0.8.7. But 0.9.1 is not the version used in cargo, which is 0.9.3. Rather than trying to match versions exactly, I just updated rustfix to the latest in the 0.8 branch.
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