Reduce visibility of MacWatchKey to package-private

Author: sungshik

src/main/java/engineering/swat/watch/impl/mac/MacWatchKey.java

@@ -43,7 +43,7 @@
 
 import com.sun.nio.file.ExtendedWatchEventModifier;
 
-public class MacWatchKey implements WatchKey {
+class MacWatchKey implements WatchKey {
     private final MacWatchable watchable;
     private final MacWatchService service;
     private final BlockingQueue<WatchEvent<?>> pendingEvents;