Disable flaky test UserCloudPolicyManagerChildTest.PolicyForChildUser

This browser test is flaky due to invalid OAuth tokens from
FakeGaiaMixin. Look into the root cause and re-enable the test when
fixed.

Bug: 1052604
Change-Id: If63ba31c03a77e1f5f9667e2a653780e1f2858a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2095203Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Toby Huang <tobyhuang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748308}

chrome/browser/chromeos/policy/user_cloud_policy_manager_chromeos_browsertest.cc

@@ -210,7 +210,10 @@ IN_PROC_BROWSER_TEST_P(UserCloudPolicyManagerTest,
 
 using UserCloudPolicyManagerChildTest = UserCloudPolicyManagerTest;
 
-IN_PROC_BROWSER_TEST_P(UserCloudPolicyManagerChildTest, PolicyForChildUser) {
+// TODO(crbug/1052604): Fix the flaky test failures related to invalid
+// FakeGaiaMixin OAuth tokens.
+IN_PROC_BROWSER_TEST_P(UserCloudPolicyManagerChildTest,
+                       DISABLED_PolicyForChildUser) {
   policy::BrowserPolicyConnector::SetNonEnterpriseDomainForTesting(
       "example.com");
   EXPECT_TRUE(policy::BrowserPolicyConnector::IsNonEnterpriseUser(