Move symfony/flex dependency to require-dev
Move symfony/flex dependency to require-dev

pjedrzejewski/Sylius,101medialab/Sylius,101medialab/Sylius,venyii/Sylius,Arminek/Sylius,foobarflies/Sylius,mbabker/Sylius,venyii/Sylius,Zales0123/Sylius,NeverResponse/Sylius,mbabker/Sylius,lchrusciel/Sylius,diimpp/Sylius,bitbager/Sylius,ezecosystem/Sylius,pamil/Sylius,NeverResponse/Sylius,ezecosystem/Sylius,gorkalaucirica/Sylius,loic425/Sylius,gseidel/Sylius,pjedrzejewski/Sylius,Brille24/Sylius,bitbager/Sylius,mbabker/Sylius,gseidel/Sylius,gorkalaucirica/Sylius,itinance/Sylius,antonioperic/Sylius,SyliusBot/Sylius,101medialab/Sylius,diimpp/Sylius,ezecosystem/Sylius,torinaki/Sylius,GSadee/Sylius,torinaki/Sylius,lchrusciel/Sylius,lchrusciel/Sylius,venyii/Sylius,foobarflies/Sylius,torinaki/Sylius,Brille24/Sylius,SyliusBot/Sylius,gseidel/Sylius,venyii/Sylius,torinaki/Sylius,ezecosystem/Sylius,bitbager/Sylius,pamil/Sylius,mbabker/Sylius,NeverResponse/Sylius,SyliusBot/Sylius,itinance/Sylius,gorkalaucirica/Sylius,bitbager/Sylius,diimpp/Sylius,NeverResponse/Sylius,Zales0123/Sylius,Sylius/Sylius,Arminek/Sylius,foobarflies/Sylius,pjedrzejewski/Sylius,kayue/Sylius,kayue/Sylius,GSadee/Sylius,kayue/Sylius,foobarflies/Sylius,gseidel/Sylius,Arminek/Sylius,Brille24/Sylius,pjedrzejewski/Sylius,Sylius/Sylius,itinance/Sylius,Brille24/Sylius,Zales0123/Sylius,antonioperic/Sylius,GSadee/Sylius,pamil/Sylius,loic425/Sylius,loic425/Sylius,gorkalaucirica/Sylius,antonioperic/Sylius,itinance/Sylius,Sylius/Sylius