Fix JDA#retrieveWebhookById

src/main/java/net/dv8tion/jda/api/JDA.java

@@ -1838,6 +1838,7 @@ default JDA setRequiredScopes(@Nonnull String... scopes)
 
     /**
      * Retrieves a {@link net.dv8tion.jda.api.entities.Webhook Webhook} by its id.
+     * <br>If the webhook does not belong to any known guild of this JDA session, it will be {@link Webhook#isPartial() partial}.
      *
      * <p>Possible {@link net.dv8tion.jda.api.requests.ErrorResponse ErrorResponses} caused by
      * the returned {@link net.dv8tion.jda.api.requests.RestAction RestAction} include the following:
@@ -1867,6 +1868,7 @@ default JDA setRequiredScopes(@Nonnull String... scopes)
 
     /**
      * Retrieves a {@link net.dv8tion.jda.api.entities.Webhook Webhook} by its id.
+     * <br>If the webhook does not belong to any known guild of this JDA session, it will be {@link Webhook#isPartial() partial}.
      *
      * <p>Possible {@link net.dv8tion.jda.api.requests.ErrorResponse ErrorResponses} caused by
      * the returned {@link net.dv8tion.jda.api.requests.RestAction RestAction} include the following:

src/main/java/net/dv8tion/jda/internal/JDAImpl.java

@@ -1014,7 +1014,7 @@ public RestAction<Webhook> retrieveWebhookById(@Nonnull String webhookId)
         {
             DataObject object = response.getObject();
             EntityBuilder builder = getEntityBuilder();
-            return builder.createWebhook(object);
+            return builder.createWebhook(object, true);
         });
     }