Revert "Switch and store keyboard layouts based on IME subtype."

This reverts commit d5f7ed9f [1].

Reason for revert:
This is the part 2 of a series of reverts to unlaunch Bug 25752812,
which aimed to improve UX but did not work well.

See I7a2ed6dd39dcd8207d3d94e12cd01d5d67ba4bb5 for the detailed reason
of revert.

 [1]: Ie88ce1ab77dbfe03ab51d89c1dc9e0a7ddbb3216

Bug: 66498367
Test: Manually done
Change-Id: I207919e3cb081d77712371f58463a5d423717c8f