Inform that Android sensors must be enabled for MobileVR support

modules/mobile_vr/doc_classes/MobileVRInterface.xml

@@ -12,6 +12,7 @@
 		if interface and interface.initialize():
 		    get_viewport().use_xr = true
 		[/codeblock]
+		[b]Note:[/b] For Android, [member ProjectSettings.input_devices/sensors/enable_accelerometer], [member ProjectSettings.input_devices/sensors/enable_gravity], [member ProjectSettings.input_devices/sensors/enable_gyroscope] and [member ProjectSettings.input_devices/sensors/enable_magnetometer] must be enabled.
 	</description>
 	<tutorials>
 	</tutorials>