Remove unused variable.

When deallocate_dependencies() is performed,
softdep_journal_freeblocks() already called cancel_allocdirect() which
should have eliminated direct dependencies for all truncated full
blocks. The indirect dependencies are allowed above, since second-
and third-level dependencies are only dealt with by the code which
frees indirect block, which happens after the inode write.

Discussed with: mckusick, jeff
Reviewed by: jeff
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks