actions: rename DEFICIENCY constant to FORMAT_VARIANT
It was not obvious what does deficieny means and every format change can't be a
deficiency. There are some format changes like compression levels, share-safe
which can't be understood at deficiencies.
This patch renames the constant to make things clearer.
Differential Revision: https://phab.mercurial-scm.org/D9664
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state