update hello_react/problem.md
update hello_react/problem.md

thebuilder/learnyoureact,kohei-takata/learnyoureact,workshopper/learnyoureact,tako-black/learnyoureact,aksharpatel47/learnyoureact,marocchino/learnyoureact,Mavmeister/learnyoureact,hvp/learnyoureact,vbdoug/learnyoureact,timguoqk/learnyoureact