InProcessTethering: set min_sdk_version

Modules contributing mainline modules (APK/APEX) should set
min_sdk_version as well as apex_available.

InProcessTethering is a part of com.android.tethering.inprocess,
therefore min_sdk_version is set.

Bug: 145796956
Bug: 150999716
Test: m
Change-Id: I655211e0b9aa4bd7cb3718b6f567f0aa1a0176a5