Camera: Document LEGACY devices not being allowed on new devices

Bug: 130315905
Test: Builds
Change-Id: Ia1380344ba73216eaf078f2480ce278e99c03820
diff --git a/camera/ndk/include/camera/NdkCameraMetadataTags.h b/camera/ndk/include/camera/NdkCameraMetadataTags.h
index 320e7b3..ef5f26c 100644
--- a/camera/ndk/include/camera/NdkCameraMetadataTags.h
+++ b/camera/ndk/include/camera/NdkCameraMetadataTags.h
@@ -8311,6 +8311,7 @@
      * fire the flash for flash power metering during precapture, and then fire the flash
      * for the final capture, if a flash is available on the device and the AE mode is set to
      * enable the flash.</p>
+     * <p>Devices that initially shipped with Android version <a href="https://developer.android.com/reference/android/os/Build.VERSION_CODES.html#Q">Q</a> or newer will not include any LEGACY-level devices.</p>
      *
      * @see ACAMERA_CONTROL_AE_PRECAPTURE_TRIGGER
      * @see ACAMERA_REQUEST_AVAILABLE_CAPABILITIES