refactor: replace golang.org/x/exp/slices with slices (#16772)

The experimental functions in `golang.org/x/exp/slices` are now
available in the standard library since Go 1.21.

Reference: https://go.dev/doc/go1.21#slices

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

coderd/provisionerdserver/provisionerdserver.go

@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"net/url"
 	"reflect"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -20,7 +21,6 @@ import (
 	semconv "go.opentelemetry.io/otel/semconv/v1.14.0"
 	"go.opentelemetry.io/otel/trace"
 	"golang.org/x/exp/maps"
-	"golang.org/x/exp/slices"
 	"golang.org/x/oauth2"
 	"golang.org/x/xerrors"
 	protobuf "google.golang.org/protobuf/proto"