Fix .m.rule.contains_user_name push rule to highlight

Signed-off-by: David Vo <david@vovo.id.au>

specification/modules/push.rst

@@ -473,6 +473,9 @@ Definition (as a ``content`` rule):
             {
                 "set_tweak": "sound",
                 "value": "default"
+            },
+            {
+                "set_tweak": "highlight"
             }
         ]
     }