Rollup merge of #102468 - RalfJung:tidy, r=jyn514

tidy: make rustc dependency error less confusing

The current wording leads to very confusing messages:
```
tidy error: Dependencies for main workspace not explicitly permitted:
* unicode-ident 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)
```
Miri is part of that workspace, and there never was a problem adding Miri dependencies. The actual error is that due to a crate bump this now showed up as a rustc dependency, and *those* are restricted.