Fix test flakiness by updating the edge resizing thickness to...

Fix test flakiness by updating the edge resizing thickness to R.dimen.desktop_mode_edge_handle after the
enable_windowing_edge_resizing flag is enabled as this edge handle
threshold is stricter (lower) than the previous R.dimen.freeform_resize_handle.

Test: atest WMShellUnitTests:DragResizeWindowGeometryTests
Fixes: 356591874
Flag: EXEMPT fixing unit test only
Change-Id: I53951a84b8a5f8deb1e9822554e4685dd873e0be