8372117: Correct the misleading comment in Character.UnicodeBlock

Reviewed-by: bpb, joehw, jlu

Author: naotoj

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

@@ -743,7 +743,8 @@ public final String toString() {
      */
     public static final class UnicodeBlock extends Subset {
         /**
-         * NUM_ENTITIES should match the total number of UnicodeBlocks.
+         * NUM_ENTITIES should match the total number of UnicodeBlock identifier
+         * names plus their aliases.
          * It should be adjusted whenever the Unicode Character Database
          * is upgraded.
          */