Update itertools requirement from 0.12 to 0.13

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] <support@github.com>

macro/Cargo.toml

@@ -15,7 +15,7 @@ proc-macro = true
 [dependencies]
 darling = "0.20"
 heck = { version = "0.5", optional = true }
-itertools = "0.12"
+itertools = "0.13"
 once_cell = "1.19"
 prettyplease = "0.2"
 proc-macro2 = "1.0"