This check is incorrect: the current shard may be looking at
the old version of tablets map:
* an accept RPC comes to replica shard 0, which is already at write_both_read_new
* the new shard is shard 1, so paxos_state::accept is called on shard 1
* shard 1 is still at "streaming" -> shards_ready_for_reads() returns old
shard 0
Fixesscylladb/scylladb#26801Closesscylladb/scylladb#26809