Remove coordinate swapping in region sampling

Captured screens for region sampling were originally rendered
upside-down, which required swapping coordinates to sample from the
correct area in the output buffer. Since then, several fixes to the
screenshot path have landed, which treat screen orientation
consistently, so the captured images are no longer upside-down. But,
the coordinate swapping was never removed. Remove it now, as sampling
during landscape is now broken.

Bug: 133849373
Bug: 241967077
Fixes: 275661349
Test: Split screen in landscape with settings app in dark mode,
calculator in light mode, and trigger back gestures

Change-Id: I52c65032d33d01a4407dc1b30215e7edac6eb1ea
(cherry picked from commit 439b6096)