cleanup from 819b26b

Motivation:
I cherry-picked 819b26b too soon. There were entries added to a deprecated class which should only go into the non-deprecated version of the class.

Modifications:
- Remove the static final variables that were added as duplicates to the deprecated class

Result:
Deprecated code does not grown in volume without need.

codec-http/src/main/java/io/netty/handler/codec/http/HttpHeaders.java

@@ -358,10 +358,6 @@ public abstract class HttpHeaders implements Iterable<Map.Entry<String, String>>
      */
     @Deprecated
     public static final class Values {
-        /**
-         * {@code "application/json"}
-         */
-        public static final String APPLICATION_JSON = "application/json";
         /**
          * {@code "application/x-www-form-urlencoded"}
          */
@@ -411,10 +407,6 @@ public abstract class HttpHeaders implements Iterable<Map.Entry<String, String>>
          * {@code "gzip"}
          */
         public static final String GZIP = "gzip";
-        /**
-         * {@code "gzip,deflate"}
-         */
-        public static final String GZIP_DEFLATE = "gzip,deflate";
         /**
          * {@code "identity"}
          */