cargo(deps): bump tokio from 1.51.1 to 1.52.0

Bumps [tokio](https://github.com/tokio-rs/tokio) from 1.51.1 to 1.52.0.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-1.51.1...tokio-1.52.0)

---
updated-dependencies:
- dependency-name: tokio
  dependency-version: 1.52.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Cargo.lock

@@ -9,7 +9,7 @@ rustmail_types = { path = "../rustmail_types" }
 serde = { version = "1.0.228", features = ["derive"] }
 serenity = "0.12.5"
 sqlx = { version = "0.8.6", features = ["runtime-tokio", "sqlite", "macros", "migrate"] }
-tokio = { version = "1.51.1", features = ["rt-multi-thread", "signal"] }
+tokio = { version = "1.52.0", features = ["rt-multi-thread", "signal"] }
 toml = "1.1.2"
 reqwest = { version = "0.13.2", features = ["json", "form"] }
 async-trait = "0.1.89"