Cargo.toml: Update multihash requirement from 0.14 to 0.15 (#50)

* Update multihash requirement from 0.14 to 0.15

Updates the requirements on [multihash](https://github.com/multiformats/rust-multihash) to permit the latest version.
- [Release notes](https://github.com/multiformats/rust-multihash/releases)
- [Commits](multiformats/rust-multihash@v0.14.0...v0.15.0)

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

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* CHANGELOG: Add entry

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Max Inden <mail@max-inden.de>

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 - Add support for TLS protocol (see [PR 48]).
 
+- Update to `multihash` `v0.15` (see [PR 50]).
+
+[PR 48]: https://github.com/multiformats/rust-multiaddr/pull/48
+[PR 50]: https://github.com/multiformats/rust-multiaddr/pull/50
+
+
 # 0.13.0 [2021-07-08]
 
 - Update to multihash v0.14.0 (see [PR 44]).

Cargo.toml

@@ -17,7 +17,7 @@ arrayref = "0.3"
 bs58 = "0.4.0"
 byteorder = "1.3.1"
 data-encoding = "2.1"
-multihash = { version = "0.14", default-features = false, features = ["std", "multihash-impl", "identity"] }
+multihash = { version = "0.15", default-features = false, features = ["std", "multihash-impl", "identity"] }
 percent-encoding = "2.1.0"
 serde = "1.0.70"
 static_assertions = "1.1"