Remove SdkVersion condition from image variants

Image variants must be based on installed partitions. SdkVersion is
orthogonal to image variants. Checking SdkVersion is legacy and it's
causing product modules to be a core variant (incorrectly).

Bug: 370351758
Test: m android_gsi
Change-Id: If496675efa5fe49207ad9c2c32b5e1cddebf1a03