lmkd: increase the soft limit for keyboard

lmkd sets the soft limit parameters for Go devices.
The limit for apps in the perceptible group is set to 16M.
However this limit is not sufficient for the keyboard app to
prevent pages from being re-claimed quickly. The mem usage of
the keyboard app is around 55M most cases with some occasional
spikes to 70-80M. Increasing the limit to 64M improves the warm
startup latency for keyboard. It is still lower than the limits
set for foreground and visible apps.

Test: Go device (1G)
Bug: 117517805
Merged-In: Id50e49327cfd76126e41ef6503971845f29196af
Change-Id: Id50e49327cfd76126e41ef6503971845f29196af