Reverted changes to README because sample is about SP2019, not SP Online.
Reverted changes to README because sample is about SP2019, not SP Online.

AJIXuMuK/sp-dev-fx-webparts,rgarita/sp-dev-fx-webparts,SharePoint/sp-dev-fx-webparts,AJIXuMuK/sp-dev-fx-webparts,SharePoint/sp-dev-fx-webparts,AJIXuMuK/sp-dev-fx-webparts,rgarita/sp-dev-fx-webparts