AP_Scripting: added set_override method for scripting

useful for test code

libraries/AP_Scripting/docs/docs.lua

@@ -679,6 +679,10 @@ local RC_Channel_ud = {}
 ---@return number
 function RC_Channel_ud:norm_input_ignore_trim() end
 
+-- desc
+---@param PWM integer
+function RC_Channel_ud:set_override(PWM) end
+
 -- desc
 ---@return integer
 function RC_Channel_ud:get_aux_switch_pos() end