vendor: update all dependencies

vendor/cloud.google.com/go/datastore/save.go

@@ -438,6 +438,10 @@ func isEmptyValue(v reflect.Value) bool {
 		return v.Float() == 0
 	case reflect.Interface, reflect.Ptr:
 		return v.IsNil()
+	case reflect.Struct:
+		if t, ok := v.Interface().(time.Time); ok {
+			return t.IsZero()
+		}
 	}
 	return false
 }