[doc] adjust upgrade message.
[doc] adjust upgrade message.

fullpipe/Payum,aitboudad/Payum,fullpipe/Payum,Payum/Payum,staabm/Payum,StoreFactory/Payum,formapro-forks/Payum,formapro-forks/Payum,digisec/Payum,ASKozienko/Payum,StoreFactory/Payum,digisec/Payum,Payum/Payum,StoreFactory/Payum