ext2: acl: remove unneeded include of linux/capability.h

acl.c has not been (directly) using the interface defined by
linux/capability.h header since commit 3bd858ab1c451725c07a
("Introduce is_owner_or_cap() to wrap CAP_FOWNER use with fsuid
check"). Remove it.

Signed-off-by: Jakub Sitnicki <jsitnicki@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>