Update tokio requirement from 0.3.0 to 1.4.0

Updates the requirements on [tokio](https://github.com/tokio-rs/tokio) to permit the latest version.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-0.3.0...tokio-1.4.0)

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

Cargo.toml

@@ -38,7 +38,7 @@ serde_derive = "1.0.115"
 postgres = { version = "0.17.5", optional = true }
 
 # feature async-psql
-tokio = { version = "0.3.0", optional = true, features = ["macros"]  }
+tokio = { version = "1.4.0", optional = true, features = ["macros"]  }
 tokio-postgres = { version = "0.5.5", optional = true }
 futures = { version = "0.3.4", optional = true }
 bytes = { version = "0.5.4", optional = true }