Add comment about when backward compat can be removed

Signed-off-by: Matt Lord <mattalord@gmail.com>

go/mysql/replication_status.go

@@ -136,11 +136,12 @@ func ProtoToReplicationStatus(s *replicationdatapb.Status) ReplicationStatus {
  }
 
  // We need to be able to process gRPC response messages from v13 and older tablets.
- // In those cases there will be no value (uknown) for the IoState or SqlState but
+ // In those cases there will be no value (unknown) for the IoState or SqlState but
  // the message will have the IoThreadRunning and SqlThreadRunning booleans and we
  // need to revert to our assumptions about a binary state as that's all the older
  // tablet can provide (really only applicable to the IO status as that is NOT binary
  // but rather has three states: Running, Stopped, Connecting).
+ // This backwards compatibility can be removed in v15+.
  if replstatus.IOState == ReplicationStateUnknown {
  if s.IoThreadRunning {
  replstatus.IOState = ReplicationStateRunning

go/vt/vtctl/reparentutil/replication.go

@@ -153,7 +153,7 @@ func ReplicaWasRunning(stopStatus *replicationdatapb.StopReplicationStatus) (boo
  // v13 and older tablets will only provide the binary IoThreadRunning and
  // SqlThreadRunning values while v14 and newer tablets will provide the
  // non-binary replication states.
- // This backwards compatible check can be removed in v15.
+ // This backwards compatible check can be removed in v15+.
  return ((stopStatus.Before.IoState == int32(mysql.ReplicationStateRunning) || stopStatus.Before.IoThreadRunning) ||
  (stopStatus.Before.SqlState == int32(mysql.ReplicationStateRunning) || stopStatus.Before.SqlThreadRunning)), nil
 }
@@ -168,7 +168,7 @@ func SQLThreadWasRunning(stopStatus *replicationdatapb.StopReplicationStatus) (b
 
  // v13 and older tablets will only provide the binary SqlThreadRunning value
  // while v14 and newer tablets will provide the non-binary replication states.
- // This backwards compatible check can be removed in v15.
+ // This backwards compatible check can be removed in v15+.
  return (stopStatus.Before.SqlState == int32(mysql.ReplicationStateRunning) || stopStatus.Before.SqlThreadRunning), nil
 }