Update docs/index.bs

Co-authored-by: Domenic Denicola <[email protected]>

docs/index.bs

@@ -3202,7 +3202,7 @@ spec: storage; urlPrefix: https://storage.spec.whatwg.org/
                       1. If |response|'s [=response/type=] is "`opaque`", and [=cross-origin resource policy check=] with |settingsObject|'s [=environment settings object/origin=], |settingsObject|, "", and |response|'s [=filtered response/internal response=] returns <b>blocked</b>, then return null.
                       1. Return |response|.
               1. Return null.
-          1. Assert: |source| is "fetch-event"
+          1. Assert: |source| is "{{RouterSourceEnum/fetch-event}}"
       1. If |request| is a [=navigation request=], |registration|'s [=navigation preload enabled flag=] is set, |request|'s [=request/method=] is \`<code>GET</code>\`, |registration|'s [=active worker=]'s [=set of event types to handle=] [=set/contains=] <code>fetch</code>, and |registration|'s [=active worker=]'s [=all fetch listeners are empty flag=] is not set then:
 
           Note: If the above is true except |registration|'s [=active worker=]'s <a>set of event types to handle</a> **does not** contain <code>fetch</code>, then the user agent may wish to show a console warning, as the developer's intent isn't clear.