Lower led bulb intensity with resistor
Your big metal film cap is is the main part that sets up led current and hence brightness . If you increase the series resistor value you will waste power to dim the lamp                .Halving C will halve the led current                        Try some lower values to get your desired level of brightness .Remember that this cap is a mains part and should be safety rated like X2 .If you do not have an assortment of caps on hand you can use your existing caps in series to ascertain your desired value for purchasing .