comment updates for clarity around RTU gateway vs RTU

supervisor/session/rtu/envd.lua

@@ -23,10 +23,10 @@ local PERIODICS = {
 
 -- create a new environment detector rtu session runner
 ---@nodiscard
----@param session_id integer
----@param unit_id integer
----@param advert rtu_advertisement
----@param out_queue mqueue
+---@param session_id integer RTU gateway session ID
+---@param unit_id integer RTU ID
+---@param advert rtu_advertisement RTU advertisement table
+---@param out_queue mqueue RTU message out queue
 function envd.new(session_id, unit_id, advert, out_queue)
     -- checks
     if advert.type ~= RTU_UNIT_TYPE.ENV_DETECTOR then