Bump strum from 0.26.2 to 0.26.3

Bumps [strum](https://github.com/Peternator7/strum) from 0.26.2 to 0.26.3.
- [Release notes](https://github.com/Peternator7/strum/releases)
- [Changelog](https://github.com/Peternator7/strum/blob/master/CHANGELOG.md)
- [Commits](Peternator7/strum@v0.26.2...v0.26.3)

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

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

Cargo.toml

@@ -1280,7 +1280,7 @@ ssz_rs_derive = { version = "0.9.0", default-features = false }
 static_assertions = { version = "1.1.0", default-features = false }
 static_init = { version = "1.0.3" }
 structopt = { version = "0.3" }
-strum = { version = "0.26.2", default-features = false }
+strum = { version = "0.26.3", default-features = false }
 subkey = { path = "substrate/bin/utils/subkey", default-features = false }
 substrate-bip39 = { path = "substrate/utils/substrate-bip39", default-features = false }
 substrate-build-script-utils = { path = "substrate/utils/build-script-utils", default-features = false }