Bump serde from 1.0.204 to 1.0.206 (#4139)

Bumps [serde](https://github.com/serde-rs/serde) from 1.0.204 to 1.0.206.
- [Release notes](https://github.com/serde-rs/serde/releases)
- [Commits](serde-rs/serde@v1.0.204...v1.0.206)

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

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

Cargo.toml

@@ -92,7 +92,7 @@ retry                    = { version = "2.0.0", default-features = false }
 ripemd                   = "0.1.3"
 secp256k1                = "0.28.2"
 semver                   = "1.0.21"
-serde                    = "1.0.204"
+serde                    = "1.0.206"
 serde_derive             = "1.0.104"
 serde_json               = "1.0.122"
 serde_yaml               = "0.9.34"