Removed the vendored git-lfs and the GitLfs build flag

AFAICS all git-annex builds are using the git-lfs library not the vendored
copy.

Debian stable now includes a new enough haskell-git-lfs package as well.
Last time this was tried it did not.

standalone/linux/stack-i386ancient.yaml

@@ -8,7 +8,6 @@ flags:
     dbus: false
     debuglocks: false
     benchmark: false
-    gitlfs: true
 packages:
 - '.'
 extra-deps: