Update itertools requirement from 0.12.0 to 0.13.0 in /test-util

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...v0.12.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

test-util/Cargo.toml

@@ -11,7 +11,7 @@ edition = "2018"
 csv = "1.1"
 conv = "0.3.3"
 include_dir = {version = "0.7.3", features = ["glob"]}
-itertools = "0.12.0"
+itertools = "0.13.0"
 lazy_static = "1.4"
 light-curve-feature = { path = "..", default-features = false }
 serde = { version = "1", features = ["derive"] }