remove unfinished doc sentence

Closes #521

logger.go

@@ -25,7 +25,7 @@ type Logger struct {
 	Formatter Formatter
 	// The logging level the logger should log at. This is typically (and defaults
 	// to) `logrus.Info`, which allows Info(), Warn(), Error() and Fatal() to be
-	// logged. `logrus.Debug` is useful in
+	// logged.
 	Level Level
 	// Used to sync writing to the log. Locking is enabled by Default
 	mu MutexWrap