Bump indexmap from 1.7.0 to 1.8.0 (#4876)

Bumps [indexmap](https://github.com/bluss/indexmap) from 1.7.0 to 1.8.0.
- [Release notes](https://github.com/bluss/indexmap/releases)
- [Changelog](https://github.com/bluss/indexmap/blob/master/RELEASES.rst)
- [Commits](indexmap-rs/indexmap@1.7.0...1.8.0)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

node/network/statement-distribution/Cargo.toml

@@ -16,7 +16,7 @@ polkadot-node-primitives = { path = "../../primitives" }
 polkadot-node-subsystem-util = { path = "../../subsystem-util" }
 polkadot-node-network-protocol = { path = "../../network/protocol" }
 arrayvec = "0.5.2"
-indexmap = "1.7.0"
+indexmap = "1.8.0"
 parity-scale-codec = { version = "2.3.1", default-features = false, features = ["derive"] }
 derive_more = "0.99.17"
 thiserror = "1.0.30"