Fix DesktopModeEventLoggerTest flakiness

The test should not care calls of FrameworkStatsLog.write() which
is not related to desktop mode.

Bug: 383548431
Flag: EXEMPT Test only change
Test: atest --rerun-until-failure 100 DesktopModeEventLoggerTest
Change-Id: I7b4772182d2344600e6d5d7a6a6ed68210f9877e