JDK 9 RFR of 8176221: Preferences docs contain reference to Sun's JRE

[Brian Burkhalter]

Please review this simple doc-only change for [1]:

--- a/src/java.prefs/share/classes/java/util/prefs/Preferences.java
+++ b/src/java.prefs/share/classes/java/util/prefs/Preferences.java
@@ -188,8 +188,8 @@
  * administrator to replace the default preferences implementation with an
  * alternative implementation.
  *
- * <p>Implementation note: In Sun's JRE, the {@code PreferencesFactory}
- * implementation is located as follows:
+ * @implNote
+ * The {@code PreferencesFactory} implementation is located as follows:
  *
  * <ol>

Thanks,

Brian

[1] https://bugs.openjdk.java.net/browse/JDK-8176221