Editorial: restore necessary comma

This comma got dropped in 83037a1 but
the sentence isn’t grammatical without it, so this change restores it.

dom.bs

@@ -278,7 +278,7 @@ function imgFetched(ev) {
 <a>Event listeners</a> can be removed
 by utilizing the
 {{EventTarget/removeEventListener()}}
-method passing the same arguments.
+method, passing the same arguments.
 
 Alternatively, <a>event listeners</a> can be removed by passing an {{AbortSignal}} to
 {{EventTarget/addEventListener()}} and calling {{AbortController/abort()}} on the controller