Remove min sdk version and set target/max sdk version to 29

Min sdk version has been force set to 28 (P) to support beta devices.
Since we now don't need to support them, we delete it. It is set to 29
by the build system.

Target and max sdk versions are bumped to 29.

Bug: 131128233
Test: m and check the sdk version numbers
Change-Id: I9ecf2b7542bde239955daf91c88b8e612d7d7069