Bump strum from 0.25.0 to 0.26.1

Bumps [strum](https://github.com/Peternator7/strum) from 0.25.0 to 0.26.1.
- [Changelog](https://github.com/Peternator7/strum/blob/master/CHANGELOG.md)
- [Commits](https://github.com/Peternator7/strum/commits)

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

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

bridges/relays/bin-substrate/Cargo.toml

@@ -23,7 +23,7 @@ rbtag = "0.3"
 structopt = "0.3"
 signal-hook = "0.3.15"
 signal-hook-async-std = "0.2.2"
-strum = { version = "0.25.0", features = ["derive"] }
+strum = { version = "0.26.1", features = ["derive"] }
 
 # Bridge dependencies
 bp-bridge-hub-polkadot = { path = "../../primitives/chain-bridge-hub-polkadot" }