Bump serde from 1.0.215 to 1.0.219 in /backend

Bumps [serde](https://github.com/serde-rs/serde) from 1.0.215 to 1.0.219.
- [Release notes](https://github.com/serde-rs/serde/releases)
- [Commits](https://github.com/serde-rs/serde/compare/v1.0.215...v1.0.219)

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

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

backend/Cargo.toml

@@ -15,7 +15,7 @@ repository = "https://github.com/schmelczer/vault-link"
 version = "0.2.2"
 
 [workspace.dependencies]  
-serde = { version = "1.0.214", default-features = false, features = ["derive"] }
+serde = { version = "1.0.219", default-features = false, features = ["derive"] }
 thiserror = { version = "1.0.66", default-features = false  } 
 
 [profile.release]