Improve `UriPermissionTest` flakiness.

Public API docs indicate that taking a grant a second time should
result in a "touch" of the `persistedCreateTime` value; we update
the test to confirm this, which was uncovered via a flaky test.

Bug: 322805216
Test: atest FrameworksServicesTestsRavenwood
Change-Id: Id5c6e6c70e639df37327b98c7647d065a2300d32
1 file changed