Bump unsigned-varint from 0.6.0 to 0.7.0

Bumps [unsigned-varint](https://github.com/paritytech/unsigned-varint) from 0.6.0 to 0.7.0.
- [Release notes](https://github.com/paritytech/unsigned-varint/releases)
- [Changelog](https://github.com/paritytech/unsigned-varint/blob/master/CHANGELOG.md)
- [Commits](paritytech/unsigned-varint@v0.6.0...v0.7.0)

---
updated-dependencies:
- dependency-name: unsigned-varint
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Cargo.lock

@@ -56,7 +56,7 @@ sp-runtime = { version = "6.0.0", path = "../../primitives/runtime" }
 sc-utils = { version = "4.0.0-dev", path = "../utils" }
 sp-finality-grandpa = { version = "4.0.0-dev", path = "../../primitives/finality-grandpa" }
 thiserror = "1.0"
-unsigned-varint = { version = "0.6.0", features = [
+unsigned-varint = { version = "0.7.0", features = [
     "futures",
     "asynchronous_codec",
 ] }