Update hashbrown requirement from 0.11.2 to 0.15.0

Updates the requirements on [hashbrown](https://github.com/rust-lang/hashbrown) to permit the latest version.
- [Changelog](https://github.com/rust-lang/hashbrown/blob/master/CHANGELOG.md)
- [Commits](rust-lang/hashbrown@v0.11.2...v0.14.5)

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

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

Cargo.toml

@@ -16,7 +16,7 @@ categories = ["data-structures", "no-std"]
 # For the default hasher
 ahash_ = { version = "0.7.0", default-features = false, optional = true, package = "ahash" }
 
-hashbrown = { version = "0.11.2", default-features = false, features = ["raw"] }
+hashbrown = { version = "0.15.0", default-features = false, features = ["raw"] }
 
 # For external trait impls
 rayon_ = { version = "1.3.0", optional = true, package = "rayon" }