Fix muzzle for rum advice (#10146)

Author: amarziali

dd-java-agent/instrumentation/servlet/javax-servlet/javax-servlet-3.0/src/main/java/datadog/trace/instrumentation/servlet3/RumAsyncContextInstrumentation.java

@@ -41,6 +41,11 @@ public ElementMatcher<TypeDescription> hierarchyMatcher() {
     return implementsInterface(named(hierarchyMarkerType()));
   }
 
+  @Override
+  public String muzzleDirective() {
+    return "servlet-3.x";
+  }
+
   @Override
   public boolean isEnabled() {
     return super.isEnabled() && InstrumenterConfig.get().isRumEnabled();