Remove obsolete Android.mk that interferes with build process. am: 0cde06079f

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/fft2d/+/13632208

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I1e2010e620eaa160f08bf9f08722702fdf9a2754