Update tracing-subscriber requirement from =0.2.12 to =0.2.17

Updates the requirements on [tracing-subscriber](https://github.com/tokio-rs/tracing) to permit the latest version.
- [Release notes](https://github.com/tokio-rs/tracing/releases)
- [Commits](tokio-rs/tracing@tracing-subscriber-0.2.12...tracing-subscriber-0.2.17)

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

Cargo.toml

@@ -96,7 +96,7 @@ static_assertions = "1.1"
 structopt = "0.3"
 tempfile = "3.1"
 test-case = "1.1"
-tracing-subscriber = "=0.2.12"
+tracing-subscriber = "=0.2.17"
 serde_json = "1"
 
 [dev-dependencies.testserver]