Have the mock log facade not always print to stdout

In #463 we introduced a mock logger that implements the `log` facade in
tests. Previously, it defaulted to always print `TRACE`-level logs to
`stdout`. This however can be very spammy (especially since it includes
TRACE-level logs of `electrum_client` now).

Here, we simply disable printing to `stdout`

Author: tnull

tests/common/logging.rs

@@ -48,7 +48,6 @@ impl LogFacadeLog for MockLogFacadeLogger {
 			record.line().unwrap(),
 			record.args()
 		);
-		println!("{message}");
 		self.logs.lock().unwrap().push(message);
 	}