Remove WMShellFlickerTestsDesktopMode CatchAll (for now)

The flicker service infra is running setup before excluding the tests. This will be addressed with b/415983232 but pushing this to unblock presubmit in the meantime

Bug: 311643481
Flag: EXEMPT Test only
Test: atest WMShellFlickerTestsDesktopMode
Change-Id: I3d33f8d71c42df9cbbde7dfcd817c3189717116c