Bump serde_with from 3.12.0 to 3.15.0 in /sync-server

Bumps [serde_with](https://github.com/jonasbb/serde_with) from 3.12.0 to 3.15.0.
- [Release notes](https://github.com/jonasbb/serde_with/releases)
- [Commits](https://github.com/jonasbb/serde_with/compare/v3.12.0...v3.15.0)

---
updated-dependencies:
- dependency-name: serde_with
  dependency-version: 3.15.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

sync-server/Cargo.toml

@@ -32,7 +32,7 @@ serde_json = "1.0.140"
 clap-verbosity-flag = "3.0.3"
 bimap = "0.6.3"
 ts-rs =  { version = "10.1", features = ["uuid-impl", "chrono-impl"] }
-serde_with = "3.12.0"
+serde_with = "3.15.0"
 base64 = "0.22.1"
 reconcile-text = "0.5.0"