Fix missing WindowTestBase.tearDown call

Bug: 116449554
Test: tradefed.sh run commandAndExit FrameworksServicesTests \
    --include-filter com.android.server.wm \
    --include-annotation android.platform.test.annotations.Presubmit \
    --exclude-annotation androidx.test.filters.FlakyTest

Change-Id: I5cb699f0f2d4e762d8712eea02577195fbaa124c
3 files changed