Add units to WINDSHIELD_WIPERS_PERIOD HAL doc

Bug: 271302606
Test: presubmit
Change-Id: I047817cf85a8516256607c15315ed8a8d94fbac2
diff --git a/automotive/vehicle/aidl_property/android/hardware/automotive/vehicle/VehicleProperty.aidl b/automotive/vehicle/aidl_property/android/hardware/automotive/vehicle/VehicleProperty.aidl
index c29076d..b628b60 100644
--- a/automotive/vehicle/aidl_property/android/hardware/automotive/vehicle/VehicleProperty.aidl
+++ b/automotive/vehicle/aidl_property/android/hardware/automotive/vehicle/VehicleProperty.aidl
@@ -2146,6 +2146,7 @@
      *
      * @change_mode VehiclePropertyChangeMode.ON_CHANGE
      * @access VehiclePropertyAccess.READ
+     * @unit VehicleUnit:MILLI_SECS
      */
     WINDSHIELD_WIPERS_PERIOD =
             0x0BC5 + VehiclePropertyGroup.SYSTEM + VehicleArea.WINDOW + VehiclePropertyType.INT32,