Remove unnecessary line in Http2ClientUpgradeCodec (#9750)

Motivation:
To clean up code.

Modification:
Remove unnecessary line.

Result:
There's no functional change.

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2ClientUpgradeCodec.java

@@ -111,7 +111,6 @@ public class Http2ClientUpgradeCodec implements HttpClientUpgradeHandler.Upgrade
     }
 
     @Override
-
     public CharSequence protocol() {
         return HTTP_UPGRADE_PROTOCOL_NAME;
     }