ANDROID: Remove obsolete -DKTEST flag from timers selftests

-DKTEST is a leftover from an old timers Makefile that is no longer
used.

Bug: 339526723
Signed-off-by: Edward Liaw <edliaw@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:b343509ebd6767934089e596d39e278ba8068669)
Merged-In: I5f353fda3452e24adb8f2539ebc7b30fd6756479
Change-Id: I5f353fda3452e24adb8f2539ebc7b30fd6756479