folder_branch_ops: add comment about fixing up LatestGCRevision
folder_branch_ops: add comment about fixing up LatestGCRevision

Issue: KBFS-1922
Issue: #756

keybase/client,keybase/client,keybase/client,keybase/client,keybase/kbfs,keybase/kbfs,keybase/client,keybase/kbfs,keybase/client,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client