update multipart-post dependency to keep 1.2 support
update multipart-post dependency to keep 1.2 support

santiagodoldan/faraday,O-I/faraday,coinbase/faraday,customink/faraday,lostisland/faraday,lostisland/faraday,nevans/faraday,engineyard/faraday,pvdb/faraday,iamjarvo/faraday,davoclavo/faraday,ru-faraon/Faraday-is-an-HTTP-client,AvaelKross/faraday,O-I/faraday,grosser/faraday,daviswahl/faraday,spyofchina/faraday,ekampp/faraday,davidcornu/faraday,prcongithub/faraday,santiagodoldan/faraday,hstrowd/faraday,daviswahl/faraday,flower-pot/faraday,engineyard/faraday,luvtechno/faraday,stayhero/faraday,apepper/faraday,prcongithub/faraday,stayhero/faraday,zanker/faraday,ngpestelos/faraday,ngpestelos/faraday,iamjarvo/faraday,hstrowd/faraday,davidcornu/faraday,hrysd/faraday,jhass/faraday,ru-faraon/Faraday-is-an-HTTP-client,apepper/faraday,jhass/faraday,grosser/faraday,pvdb/faraday,zhaoxl/faraday,jrafanie/faraday,davoclavo/faraday,mauricionr/faraday,customink/faraday,coinbase/faraday,ekampp/faraday,zhaoxl/faraday,AvaelKross/faraday,mehulkar/faraday,luvtechno/faraday,hrysd/faraday,jrafanie/faraday,flower-pot/faraday,mauricionr/faraday,mehulkar/faraday,spyofchina/faraday,zanker/faraday,nevans/faraday