clusterversion,kv: remove NonVotingReplicas

Partially addresses cockroachdb#66544 by removing a cluster version and its associated
dependencies which, for any cluster whose version is at least 21.1, is certain
to be active.

Release justification: cluster version cleanup

pkg/clusterversion/cockroach_versions.go

@@ -210,8 +210,6 @@ const (
 	// are propagated across RPC boundaries independently of their verbosity setting.
 	// This requires a version gate this violates implicit assumptions in v20.2.
 	TracingVerbosityIndependentSemantics
-	// NonVotingReplicas enables the creation of non-voting replicas.
-	NonVotingReplicas
 	// V21_1 is CockroachDB v21.1. It's used for all v21.1.x patch releases.
 	V21_1
 
@@ -371,10 +369,6 @@ var versionsSingleton = keyedVersions{
 		Key:     TracingVerbosityIndependentSemantics,
 		Version: roachpb.Version{Major: 20, Minor: 2, Internal: 28},
 	},
-	{
-		Key:     NonVotingReplicas,
-		Version: roachpb.Version{Major: 20, Minor: 2, Internal: 46},
-	},
 	{
 		// V21_1 is CockroachDB v21.1. It's used for all v21.1.x patch releases.
 		Key:     V21_1,

pkg/kv/kvserver/replicate_queue.go

@@ -18,7 +18,6 @@ import (
 	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/base"
-	"github.com/cockroachdb/cockroach/pkg/clusterversion"
 	"github.com/cockroachdb/cockroach/pkg/gossip"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/kvserverpb"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/liveness/livenesspb"
@@ -661,11 +660,6 @@ func (rq *replicateQueue) addOrReplaceNonVoters(
 	removeIdx int,
 	dryRun bool,
 ) (requeue bool, _ error) {
-	// Non-voter creation is disabled before 21.1.
-	if v, st := clusterversion.NonVotingReplicas, repl.ClusterSettings(); !st.Version.IsActive(ctx, v) {
-		return false, errors.AssertionFailedf("non-voting replicas cannot be created pre-21.1")
-	}
-
 	desc, conf := repl.DescAndSpanConfig()
 	existingNonVoters := desc.Replicas().NonVoterDescriptors()
 

pkg/sql/set_zone_config.go

@@ -17,7 +17,6 @@ import (
 	"strings"
 
 	"github.com/cockroachdb/cockroach/pkg/base"
-	"github.com/cockroachdb/cockroach/pkg/clusterversion"
 	"github.com/cockroachdb/cockroach/pkg/config"
 	"github.com/cockroachdb/cockroach/pkg/config/zonepb"
 	"github.com/cockroachdb/cockroach/pkg/keys"
@@ -78,9 +77,6 @@ var supportedZoneConfigOptions = map[tree.Name]struct {
 		requiredType: types.Bool,
 		setter:       func(c *zonepb.ZoneConfig, d tree.Datum) { c.GlobalReads = proto.Bool(bool(tree.MustBeDBool(d))) },
 		checkAllowed: func(ctx context.Context, execCfg *ExecutorConfig, d tree.Datum) error {
-			if err := checkVersionActive(ctx, execCfg, clusterversion.NonVotingReplicas, "global_reads"); err != nil {
-				return err
-			}
 			if !tree.MustBeDBool(d) {
 				// Always allow the value to be unset.
 				return nil
@@ -100,9 +96,6 @@ var supportedZoneConfigOptions = map[tree.Name]struct {
 	"num_voters": {
 		requiredType: types.Int,
 		setter:       func(c *zonepb.ZoneConfig, d tree.Datum) { c.NumVoters = proto.Int32(int32(tree.MustBeDInt(d))) },
-		checkAllowed: func(ctx context.Context, execCfg *ExecutorConfig, _ tree.Datum) error {
-			return checkVersionActive(ctx, execCfg, clusterversion.NonVotingReplicas, "num_voters")
-		},
 	},
 	"gc.ttlseconds": {
 		requiredType: types.Int,
@@ -133,9 +126,6 @@ var supportedZoneConfigOptions = map[tree.Name]struct {
 			c.VoterConstraints = voterConstraintsList.Constraints
 			c.NullVoterConstraintsIsEmpty = true
 		},
-		checkAllowed: func(ctx context.Context, execCfg *ExecutorConfig, _ tree.Datum) error {
-			return checkVersionActive(ctx, execCfg, clusterversion.NonVotingReplicas, "voter_constraints")
-		},
 	},
 	"lease_preferences": {
 		requiredType: types.String,
@@ -164,16 +154,6 @@ func loadYAML(dst interface{}, yamlString string) {
 	}
 }
 
-func checkVersionActive(
-	ctx context.Context, execCfg *ExecutorConfig, minVersion clusterversion.Key, option string,
-) error {
-	if !execCfg.Settings.Version.IsActive(ctx, minVersion) {
-		return pgerror.Newf(pgcode.FeatureNotSupported,
-			"%s cannot be used until cluster version is finalized", option)
-	}
-	return nil
-}
-
 func (p *planner) SetZoneConfig(ctx context.Context, n *tree.SetZoneConfig) (planNode, error) {
 	if err := checkSchemaChangeEnabled(
 		ctx,