InputDevice: remove touchpad gestures library flag

This flag has been defaulting to true since Android 14 was released, and
we've not seen any issues that required us to revert to the old stack.

Bug: 281840344
Test: check connected touchpads work
Test: atest inputflinger_tests
Change-Id: I62e1ed0bb9adcefaa176ce921eaa1c1ba3818ec9