AppArmor: remove af_names.h from .gitignore

Commit 4fdef218 ("AppArmor: Cleanup make
file to remove cruft and make it easier to read") removed all traces of
af_names.h from the tree. Remove its entry in AppArmor's .gitignore file
too.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>