upgrade google.golang.org/grpc/health/grpc_health_v1 (#5605)

## Summary
Upgrade `google.golang.org/grpc/health/grpc_health_v1` which has a new
`List` method, so use the `UnimplementedHealthServer`.

## Related issues
- https://github.com/pomerium/ingress-controller/pull/1152

## User Explanation

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change doesn't create any user-facing changes, you can leave
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## Checklist

- [ ] reference any related issues
- [ ] updated unit tests
- [ ] add appropriate label (`enhancement`, `bug`, `breaking`,
`dependencies`, `ci`)
- [x] ready for review

pkg/grpc/health.go

@@ -3,31 +3,25 @@ package grpc
 import (
 	"context"
 
-	"google.golang.org/grpc/codes"
-	grpc_health "google.golang.org/grpc/health/grpc_health_v1"
-	"google.golang.org/grpc/status"
+	"google.golang.org/grpc/health/grpc_health_v1"
 
 	"github.com/pomerium/pomerium/internal/log"
 )
 
-type healthCheckSrv struct{}
+type healthCheckSrv struct {
+	grpc_health_v1.UnimplementedHealthServer
+}
 
 // NewHealthCheckServer returns a basic health checker
-func NewHealthCheckServer() grpc_health.HealthServer {
+func NewHealthCheckServer() grpc_health_v1.HealthServer {
 	return &healthCheckSrv{}
 }
 
 // Check confirms service is reachable, and assumes any service is operational
 // an outlier detection should be used to detect runtime malfunction based on consequitive 5xx
-func (h *healthCheckSrv) Check(ctx context.Context, req *grpc_health.HealthCheckRequest) (*grpc_health.HealthCheckResponse, error) {
+func (h *healthCheckSrv) Check(ctx context.Context, req *grpc_health_v1.HealthCheckRequest) (*grpc_health_v1.HealthCheckResponse, error) {
 	log.Ctx(ctx).Debug().Str("service", req.Service).Msg("health check")
-	return &grpc_health.HealthCheckResponse{
-		Status: grpc_health.HealthCheckResponse_SERVING,
+	return &grpc_health_v1.HealthCheckResponse{
+		Status: grpc_health_v1.HealthCheckResponse_SERVING,
 	}, nil
 }
-
-// Watch is not implemented as is not used by Envoy
-func (h *healthCheckSrv) Watch(req *grpc_health.HealthCheckRequest, _ grpc_health.Health_WatchServer) error {
-	log.Error().Str("service", req.Service).Msg("health check watch")
-	return status.Errorf(codes.Unimplemented, "method Watch not implemented")
-}