rpc: remove env variable requirement to change drpc setting

Previously, we required `COCKROACH_EXPERIMENTAL_DRPC_ENABLED` to be set to
enable the DRPC cluster setting. In version 25.4, we want to give customers
the ability to use this setting without needing the environment variable.

Epic: CRDB-52378
Release note: none

Author: shubhamdhama

pkg/rpc/rpcbase/BUILD.bazel

@@ -27,9 +27,7 @@ go_library(
         "//pkg/rpc/rpcpb",
         "//pkg/settings",
         "//pkg/settings/cluster",
-        "//pkg/util/buildutil",
         "//pkg/util/envutil",
-        "@com_github_cockroachdb_errors//:errors",
         "@io_storj_drpc//:drpc",
         "@org_golang_google_grpc//:grpc",
     ],

pkg/rpc/rpcbase/nodedialer.go

@@ -11,9 +11,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/settings"
 	"github.com/cockroachdb/cockroach/pkg/settings/cluster"
-	"github.com/cockroachdb/cockroach/pkg/util/buildutil"
 	"github.com/cockroachdb/cockroach/pkg/util/envutil"
-	"github.com/cockroachdb/errors"
 	"google.golang.org/grpc"
 	"storj.io/drpc"
 )
@@ -27,17 +25,7 @@ var ExperimentalDRPCEnabled = settings.RegisterBoolSetting(
 	settings.ApplicationLevel,
 	"rpc.experimental_drpc.enabled",
 	"if true, use drpc to execute Batch RPCs (instead of gRPC)",
-	envExperimentalDRPCEnabled,
-	settings.WithValidateBool(func(values *settings.Values, b bool) error {
-		// drpc support is highly experimental and should not be enabled in production.
-		// Since authorization is not implemented, we only even host the server if the
-		// env var is set or it's a CRDB test build. Consequently, these are prereqs
-		// for setting the cluster setting.
-		if b && !(envExperimentalDRPCEnabled || buildutil.CrdbTestBuild) {
-			return errors.New("experimental drpc is not allowed in this environment")
-		}
-		return nil
-	}))
+	envExperimentalDRPCEnabled)
 
 // NodeDialer interface defines methods for dialing peer nodes using their
 // node IDs.