Release region after updating touchable region

remove_status_bar_input_layer flag is currently cauing a memory
regression. The only thing being created is the Region which, if not
properly recycled, can cause mem leaks.

Bug: 441740378
Flag: com.android.window.flags.enable_remove_status_bar_input_layer
Test: manual testing
Change-Id: I8f8d6badef94fdb0e0da6686cd9f412f03986910