chore(deps): bump the backend-dependencies group

Bumps the backend-dependencies group in /backend with 3 updates: [serde_json](https://github.com/serde-rs/json), [tokio](https://github.com/tokio-rs/tokio) and [env_logger](https://github.com/rust-cli/env_logger).


Updates `serde_json` from 1.0.120 to 1.0.121
- [Release notes](https://github.com/serde-rs/json/releases)
- [Commits](serde-rs/json@v1.0.120...v1.0.121)

Updates `tokio` from 1.38.1 to 1.39.2
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-1.38.1...tokio-1.39.2)

Updates `env_logger` from 0.11.3 to 0.11.5
- [Release notes](https://github.com/rust-cli/env_logger/releases)
- [Changelog](https://github.com/rust-cli/env_logger/blob/main/CHANGELOG.md)
- [Commits](rust-cli/env_logger@v0.11.3...v0.11.5)

---
updated-dependencies:
- dependency-name: serde_json
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: backend-dependencies
- dependency-name: tokio
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: backend-dependencies
- dependency-name: env_logger
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: backend-dependencies
...

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

backend/Cargo.toml

@@ -19,7 +19,7 @@ serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 tokio = { version = "1", features = ["full"] }
 log = "0.4"
-env_logger = "0.11.3"
+env_logger = "0.11.5"
 
 [profile.release]
 strip = true