Update pretty_env_logger requirement from 0.3 to 0.4

Updates the requirements on [pretty_env_logger](https://github.com/seanmonstar/pretty-env-logger) to permit the latest version.
- [Release notes](https://github.com/seanmonstar/pretty-env-logger/releases)
- [Commits](seanmonstar/pretty-env-logger@v0.3.0...v0.4.0)

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

Author: dependabot-preview[bot]

Cargo.toml

@@ -9,7 +9,7 @@ default = []
 [dependencies]
 structopt = "0.3"
 log = "0.4"
-pretty_env_logger = "0.3"
+pretty_env_logger = "0.4"
 crossbeam-channel = "0.4"
 
 av-data = "0.2"