Add suggestion to use "no-cors" with Fetch fails CORS check.

LayoutTests/http/tests/fetch/chromium/error-messages-expected.txt

Index: LayoutTests/http/tests/fetch/chromium/error-messages-expected.txt
diff --git a/LayoutTests/http/tests/fetch/chromium/error-messages-expected.txt b/LayoutTests/http/tests/fetch/chromium/error-messages-expected.txt
index de1634e0cdfae8641056deb35471b6d1c8ca8f35..8e220c41450b002836c04ae8b0aefc17346161d6 100644
--- a/LayoutTests/http/tests/fetch/chromium/error-messages-expected.txt
+++ b/LayoutTests/http/tests/fetch/chromium/error-messages-expected.txt
@@ -1,4 +1,4 @@
-CONSOLE ERROR: Fetch API cannot load http://localhost:8000/fetch/resources/doctype.html. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://127.0.0.1:8000' is therefore not allowed access.
+CONSOLE ERROR: Fetch API cannot load http://localhost:8000/fetch/resources/doctype.html. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://127.0.0.1:8000' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
 CONSOLE ERROR: Fetch API cannot load http://localhost:8000/fetch/resources/redirect-loop.php?Count=100&ACAOrigin=*. Redirect failed.
 This is a testharness.js-based test.
 PASS fetch() with 200 should not output error messages