8365887: Outdated comments in String::decode

Reviewed-by: liach, sherman

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

@@ -671,14 +671,6 @@ public final class String
     }
 
     private static String decode(Charset charset, byte[] bytes, int offset, int length) {
-        // (1)We never cache the "external" cs, the only benefit of creating
-        // an additional StringDe/Encoder object to wrap it is to share the
-        // de/encode() method. These SD/E objects are short-lived, the young-gen
-        // gc should be able to take care of them well. But the best approach
-        // is still not to generate them if not really necessary.
-        // (2)The defensive copy of the input byte/char[] has a big performance
-        // impact, as well as the outgoing result byte/char[]. Need to do the
-        // optimization check of (sm==null && classLoader0==null) for both.
         CharsetDecoder cd = charset.newDecoder();
         // ArrayDecoder fastpaths
         if (cd instanceof ArrayDecoder ad) {