We need at least 6.16 to test MADV_GUARD_INSTALL support, but
our current Fedora Rawhide test uses only Rawhide's user space,
while using Fedora 42 kernel. Let's start using a vanilla kernel.
Suggested-by: Adrian Reber <areber@redhat.com>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>