Add diff-filter=d to lefthook files config

Description

I also think it should have --diff-filter=d in order to avoid running on deleted files.

I am unfamiliar with --diff-filter=d but looking at it sounds right to me to have it. Deleted paths should not have a file there, so it makes sense to exclude those from being checked.

Adding diff-filter=d to the files entries in lefthook.yml should prevent the rules from running over removed files.