Set minimum width and height in flicker test to match the actual

R.dimen.desktop_mode_minimum_window_width and
R.dimen.desktop_mode_minimum_window_height

Fixes: 363232054
Flag: EXEMPT fixing test
Test: atest WMShellFlickerTestsDesktopMode:com.android.wm.shell.flicker.ResizeAppToMinimumWindowSizeLandscape
Change-Id: I6f15270e8aa33e11f9aac18a6b346658955bfff9