Sensor HAL: Update HEART_RATE permission documentation.

Replacing the use of a specific permission with the note that the
framework will override the permission used to ensure compatibility with
the given SDK vesrion.

Change-Id: Id30d3485a920aace131f5fd609e86331b6f2c7c9
Bug: 372749975
Flag: DOCS_ONLY
diff --git a/sensors/aidl/android/hardware/sensors/SensorType.aidl b/sensors/aidl/android/hardware/sensors/SensorType.aidl
index adaf8e6..bc1b4b2 100644
--- a/sensors/aidl/android/hardware/sensors/SensorType.aidl
+++ b/sensors/aidl/android/hardware/sensors/SensorType.aidl
@@ -275,8 +275,9 @@
      *  than every period_ns passed to setDelay() or to batch().
      *  See the definition of the on-change reporting mode for more information.
      *
-     *  SensorInfo.requiredPermission must be set to
-     *  SENSOR_PERMISSION_BODY_SENSORS.
+     *  The framework will override the SensorInfo.requiredPermission to either
+     *  SENSOR_PERMISSION_BODY_SENSORS or SENSOR_PERMISSION_READ_HEART_RATE
+     *  depending on the platform SDK version in order to ensure compatibility.
      *
      *  Both wake-up and non wake-up versions are useful.
      */