Use undefined union for getRegistration()/match()/get() (#1559)

Thanks to whatwg/webidl#906.

Author: saschanaz

docs/index.bs

@@ -667,7 +667,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
 
         [NewObject] Promise<ServiceWorkerRegistration> register(USVString scriptURL, optional RegistrationOptions options = {});
 
-        [NewObject] Promise<any> getRegistration(optional USVString clientURL = "");
+        [NewObject] Promise<(ServiceWorkerRegistration or undefined)> getRegistration(optional USVString clientURL = "");
         [NewObject] Promise<FrozenArray<ServiceWorkerRegistration>> getRegistrations();
 
         undefined startMessages();
@@ -1275,7 +1275,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
       [Exposed=ServiceWorker]
       interface Clients {
         // The objects returned will be new instances every time
-        [NewObject] Promise<any> get(DOMString id);
+        [NewObject] Promise<(Client or undefined)> get(DOMString id);
         [NewObject] Promise<FrozenArray<Client>> matchAll(optional ClientQueryOptions options = {});
         [NewObject] Promise<WindowClient?> openWindow(USVString url);
         [NewObject] Promise<undefined> claim();
@@ -1814,7 +1814,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
     <pre class="idl">
       [SecureContext, Exposed=(Window,Worker)]
       interface Cache {
-        [NewObject] Promise&lt;any&gt; match(RequestInfo request, optional CacheQueryOptions options = {});
+        [NewObject] Promise&lt;(Response or undefined)&gt; match(RequestInfo request, optional CacheQueryOptions options = {});
         [NewObject] Promise&lt;FrozenArray&lt;Response&gt;&gt; matchAll(optional RequestInfo request, optional CacheQueryOptions options = {});
         [NewObject] Promise&lt;undefined&gt; add(RequestInfo request);
         [NewObject] Promise&lt;undefined&gt; addAll(sequence&lt;RequestInfo&gt; requests);
@@ -2073,7 +2073,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
     <pre class="idl">
       [SecureContext, Exposed=(Window,Worker)]
       interface CacheStorage {
-        [NewObject] Promise&lt;any&gt; match(RequestInfo request, optional MultiCacheQueryOptions options = {});
+        [NewObject] Promise&lt;(Response or undefined)&gt; match(RequestInfo request, optional MultiCacheQueryOptions options = {});
         [NewObject] Promise&lt;boolean&gt; has(DOMString cacheName);
         [NewObject] Promise&lt;Cache&gt; open(DOMString cacheName);
         [NewObject] Promise&lt;boolean&gt; delete(DOMString cacheName);