Update mockall requirement from 0.11 to 0.13

Updates the requirements on [mockall](https://github.com/asomers/mockall) to permit the latest version.
- [Changelog](https://github.com/asomers/mockall/blob/master/CHANGELOG.md)
- [Commits](asomers/mockall@v0.11.0...v0.13.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

metrics-util/Cargo.toml

@@ -79,7 +79,7 @@ tracing-subscriber = { version = "0.3", default-features = false, features = ["f
 crossbeam-queue = "0.3"
 quickcheck = "1"
 quickcheck_macros = "1"
-mockall = "0.11"
+mockall = "0.13"
 
 [features]
 handles = ["crossbeam-epoch", "crossbeam-utils"]