chore(cargo): bump criterion from 0.5.1 to 0.6.0

Bumps [criterion](https://github.com/bheisler/criterion.rs) from 0.5.1 to 0.6.0.
- [Changelog](https://github.com/bheisler/criterion.rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/bheisler/criterion.rs/compare/0.5.1...0.6.0)

---
updated-dependencies:
- dependency-name: criterion
  dependency-version: 0.6.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Co-authored-by: iequidoo <dgreshilov@gmail.com>

benches/receive_emails.rs

@@ -1,7 +1,8 @@
 #![recursion_limit = "256"]
+use std::hint::black_box;
 use std::path::PathBuf;
 
-use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use criterion::{criterion_group, criterion_main, Criterion};
 use deltachat::{
     config::Config,
     context::Context,