skip manual linux-image version inspection

Those are typically trashed at the end and overlap with the following
dsa-check-packages.

howto/upgrades/bookworm.md

@@ -103,8 +103,6 @@ See the "conflicts resolution" section below for how to handle
         : purge removed packages &&
         apt purge $(dpkg -l | awk '/^rc/ { print $2 }') &&
         apt autoremove -y --purge &&
-        : possibly clean up old kernels &&
-        dpkg -l 'linux-image-*' &&
         : look for packages from backports, other suites or archives &&
         : if possible, switch to official packages by disabling third-party repositories &&
         dsa-check-packages | tr -d , &&