btrfs: remove duplicated metadata folio flag update in end_bbio_meta_read()

In that function we call set_extent_buffer_uptodate() or
clear_extent_buffer_uptodate(), which will already update the uptodate
flag for all the involved extent buffer folios.

Thus there is no need to update the folio uptodate flags again.

Just remove the open-coded part.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>