8023943: Method description fix for String.toLower/UpperCase() methods

Reviewed-by: okutsu

src/share/classes/java/lang/String.java

@@ -2652,7 +2652,7 @@ public final class String
      * returns {@code "t\u005Cu0131tle"}, where '\u005Cu0131' is the
      * LATIN SMALL LETTER DOTLESS I character.
      * To obtain correct results for locale insensitive strings, use
-     * {@code toLowerCase(Locale.ENGLISH)}.
+     * {@code toLowerCase(Locale.ROOT)}.
      * <p>
      * @return  the {@code String}, converted to lowercase.
      * @see     java.lang.String#toLowerCase(Locale)
@@ -2815,7 +2815,7 @@ public final class String
      * returns {@code "T\u005Cu0130TLE"}, where '\u005Cu0130' is the
      * LATIN CAPITAL LETTER I WITH DOT ABOVE character.
      * To obtain correct results for locale insensitive strings, use
-     * {@code toUpperCase(Locale.ENGLISH)}.
+     * {@code toUpperCase(Locale.ROOT)}.
      * <p>
      * @return  the {@code String}, converted to uppercase.
      * @see     java.lang.String#toUpperCase(Locale)