Network Service: Recategorize some webRequest auth events related browser tests

This CL moves two webRequest auth events related browser tests to a new
category.

Bug: 841827
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I09d64ad7aef47c5388151b7e7ae50b0db382cfb1
Reviewed-on: https://chromium-review.googlesource.com/1060306Reviewed-by: Ken Rockot <rockot@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Jun Cai <juncai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558901}

testing/buildbot/filters/mojo.fyi.network_browser_tests.filter

@@ -6,8 +6,6 @@
 # See https://crbug.com/769401
 
 # Uncategorized timeouts or test failures.
--BackgroundXhrTest.HttpAuth
--BackgroundXhrTest.TlsClientAuth
 -ChromeSecurityExploitBrowserTest.CreateFilesystemURLInExtensionOrigin
 -DisabledSignInIsolationBrowserTest.SyntheticTrial
 -DomainReliabilityBrowserTest.Upload
@@ -146,6 +144,9 @@
 -ExtensionWebRequestApiTest.WebRequestClientsGoogleComProtection
 # Note WebRequestUnloadImmediately is disabled on Linux
 -ExtensionWebRequestApiTest.WebRequestUnloadImmediately
+# http://crbug.com/841827
+-BackgroundXhrTest.HttpAuth
+-BackgroundXhrTest.TlsClientAuth
 
 # https://crbug.com/721400
 # WebSocket with the network service