Update hashbrown requirement from 0.11 to 0.12 in /lightning-invoice

Updates the requirements on [hashbrown](https://github.com/rust-lang/hashbrown) to permit the latest version.
- [Release notes](https://github.com/rust-lang/hashbrown/releases)
- [Changelog](https://github.com/rust-lang/hashbrown/blob/master/CHANGELOG.md)
- [Commits](rust-lang/hashbrown@v0.11.0...v0.12.0)

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

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

Author: dependabot[bot]

lightning-invoice/Cargo.toml

@@ -23,7 +23,7 @@ lightning = { version = "0.0.106", path = "../lightning", default-features = fal
 secp256k1 = { version = "0.20", default-features = false, features = ["recovery", "alloc"] }
 num-traits = { version = "0.2.8", default-features = false }
 bitcoin_hashes = { version = "0.10", default-features = false }
-hashbrown = { version = "0.11", optional = true }
+hashbrown = { version = "0.12", optional = true }
 core2 = { version = "0.3.0", default-features = false, optional = true }
 
 [dev-dependencies]