bcachefs: Delete old faulty bch2_trans_unlock() call

the unlock is now in read_extent, this fixes an assertion pop in
read_from_stale_dirty_pointer()
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/io_read.c

@@ -389,7 +389,6 @@ static void bch2_read_retry_nodecode(struct bch_fs *c, struct bch_read_bio *rbio
 
 	bch2_bkey_buf_reassemble(&sk, c, k);
 	k = bkey_i_to_s_c(sk.k);
-	bch2_trans_unlock(trans);
 
 	if (!bch2_bkey_matches_ptr(c, k,
 				   rbio->pick.ptr,