Correctly set min SDK version for AutoRevokeSApp.

So that our S module + S MTS can pass on master.

min_sdk_version can only be set in Android.bp while target_sdk_version
can be set in either Android.bp or AndroidManifest.xml. To avoid
confusion, just set them both in Android.bp and remove them in
AndroidManifest.xml.

Bug: 183459058
Test: presubmit
Change-Id: If0057d9924f9218fad453fe84c736352b5b2d6d6