Revert "disable filter.annex.process in restagePointerFile"

Revert "disable filter.annex.process in restagePointerFile"

This reverts commit afe327ac4947d6d32ff888e7485509be03d9baaf.

Unfortunately, disabling it by setting it to "" does not work, git
then ignores filter.annex.smudge/clean, and does not pass files through
git-annex at all.

I don't think there is a way to temporarily disable this git config
from the git command line. Which seems like a bug in git.

So, it may be more expensive than anticipated to enable
filter.annex.process, since git checkout etc will pipe all annexed files
being checked out through it.