bcachefs: Fix accounting read + device removal

bcachefs: Fix accounting read + device removal

accounting read was checking if accounting replicas entries were marked
in the superblock prior to applying accounting from the journal,
which meant that a recently removed device could spuriously trigger a
"not marked in superblocked" error (when journal entries zero out the
offending counter).

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>