Auto merge of #6696 - dtolnay-contrib:regex, r=Manishearth

Downgrade trivial_regex to nursery

See #6690. I think there is still value in a trivial_regex lint, but only if clippy can tell that the regex is only ever constructed and applied to a single input.

```rust
let regex = Regex::new("trivial_regex")?;
println!("{}", regex.is_match(s));
// `regex` never used again
```

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changelog: remove `trivial_regex` from default set of enabled lints

0 files changed, 0 insertions, 0 deletions