remove static per review comment

Author: Vladimir Kotal

opengrok-web/src/main/java/org/opengrok/web/WebappListener.java

@@ -58,7 +58,7 @@ public final class WebappListener
     private static final Logger LOGGER = LoggerFactory.getLogger(WebappListener.class);
 
     private static final String TIMER_ATTR_NAME = "request_start";
-    private static Timer requestTimer;
+    private Timer requestTimer;
 
     /**
      * {@inheritDoc}