VtsBootconfigTest: enforce requirement from U+

We used to allow devices to launch with some kernels from up to two desert
releases prior. So Android 13 devices may still launch with android11-5.4
kernel which does not have bootconfig support.

The oldest kernel allowed for Android 14 launches is android12-5.10
so we can expect bootconfig suport on all Android 14 launch devices.

This change stops requiring bootconfig on Android 13 devices, and only
starts enforcing the requirement on Android 14 launch devices.

https://source.android.com/docs/core/architecture/kernel/android-common#feature-and-launch-kernels

Test: atest VtsBootconfigTest
Bug: 375051034
(cherry picked from https://android-review.googlesource.com/q/commit:c6fe7536ea16ee82337ebe536697e440b861b6c6)
Merged-In: I3012fff70eb8a27bb81aab056817d72ac559f8d2
Change-Id: I3012fff70eb8a27bb81aab056817d72ac559f8d2