Remove timer_delete_multiple test.

According to posix, this test invokes undefined behavior by deleting
a timer twice.

According to hwasan, the second call to timer_delete loads
kernel_timer_id from previously deallocated PosixTimer (i.e.
heap-use-after-free).

Bug: 114279110
Test: bionic-unit-tests with hwasan

Change-Id: Ic54579e3bb41d3f38282b8822dafaba51efd003a