Update itertools requirement from 0.12 to 0.13 (#39)

Updates the requirements on [itertools](https://github.com/rust-itertools/itertools) to permit the latest version.
- [Changelog](https://github.com/rust-itertools/itertools/blob/master/CHANGELOG.md)
- [Commits](rust-itertools/itertools@v0.12.0...v0.13.0)

---
updated-dependencies:
- dependency-name: itertools
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Cargo.toml

@@ -13,7 +13,7 @@ rust-version = "1.56.0"
 [dependencies]
 sha2 = "0.10"
 lazy_static = "1.4"
-itertools = "0.12"
+itertools = "0.13"
 rand = "0.8"
 # We pin these so they can't vary accidentally.
 unidecode = "=0.3.0"