ppb_url_loader: fix "Referer" HTTP header name
ppb_url_loader: fix "Referer" HTTP header name

reuben/freshplayerplugin,grevutiu-gabriel/freshplayerplugin,Papapashu/freshplayerplugin,grevutiu-gabriel/freshplayerplugin,reuben/freshplayerplugin,reuben/freshplayerplugin,Papapashu/freshplayerplugin,Papapashu/freshplayerplugin