Update env_logger requirement from 0.7 to 0.8

Updates the requirements on [env_logger](https://github.com/env-logger-rs/env_logger) to permit the latest version.
- [Release notes](https://github.com/env-logger-rs/env_logger/releases)
- [Changelog](https://github.com/env-logger-rs/env_logger/blob/master/CHANGELOG.md)
- [Commits](rust-cli/env_logger@v0.7.0...v0.8.1)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

tokio-postgres/Cargo.toml

@@ -54,7 +54,7 @@ tokio-util = { version = "0.4", features = ["codec"] }
 
 [dev-dependencies]
 tokio = { version = "0.3", features = ["full"] }
-env_logger = "0.7"
+env_logger = "0.8"
 criterion = "0.3"
 
 bit-vec-06 = { version = "0.6", package = "bit-vec" }