8317264: Pattern.Bound has static fields that should be static final.

Backport-of: ecb5e8a03f67c92d7956201de1fa7d07cc6af9cb

Author: rm-gh-8

src/java.base/share/classes/java/util/regex/Pattern.java

@@ -5364,10 +5364,10 @@ boolean match(Matcher matcher, int i, CharSequence seq) {
      * they are ignored for purposes of finding word boundaries.
      */
     static final class Bound extends Node {
-        static int LEFT = 0x1;
-        static int RIGHT= 0x2;
-        static int BOTH = 0x3;
-        static int NONE = 0x4;
+        static final int LEFT = 0x1;
+        static final int RIGHT= 0x2;
+        static final int BOTH = 0x3;
+        static final int NONE = 0x4;
         int type;
         boolean useUWORD;
         Bound(int n, boolean useUWORD) {