Ignore falsing manager for UiAutomator tests

Device performance and dropped frames on cloud devices makes it very
likely that touches will be misinterpreted, increasing flakiness of
the tests.

Bug: 149828540
Test: atest --test-mapping frameworks/base/packages/SystemUI:platinum-postsubmit
Change-Id: Ia9b4152b2662fa5a7442cacfd1a87064b037ea0c