doc: admin-guide/kernel-parameters: remove useless comment

This comment about DRM drivers has been there since the first git
commit. It simply doesn't belong in kernel-parameters; remove it.

Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240111085220.3693059-1-vegard.nossum@oracle.com