[CircleCI] Bump required version to iOS 8.3.
[CircleCI] Bump required version to iOS 8.3.

CircleCI does not print the assertion message, so this is just a guess.

gaurav1981/eigen,neonichu/eigen,artsy/eigen,ichu501/eigen,TribeMedia/eigen,mbogh/eigen,ayunav/eigen,ACChe/eigen,mbogh/eigen,ACChe/eigen,ayunav/eigen,ppamorim/eigen,artsy/eigen,1aurabrown/eigen,1aurabrown/eigen,ayunav/eigen,Shawn-WangDapeng/eigen,gaurav1981/eigen,zhuzhengwei/eigen,ashkan18/eigen,liduanw/eigen,ACChe/eigen,neonichu/eigen,foxsofter/eigen,gaurav1981/eigen,foxsofter/eigen,artsy/eigen,ichu501/eigen,Shawn-WangDapeng/eigen,gaurav1981/eigen,1aurabrown/eigen,mbogh/eigen,srrvnn/eigen,ashkan18/eigen,ACChe/eigen,Shawn-WangDapeng/eigen,orta/eigen,artsy/eigen,ashkan18/eigen,ayunav/eigen,ashkan18/eigen,liduanw/eigen,Shawn-WangDapeng/eigen,foxsofter/eigen,TribeMedia/eigen,artsy/eigen,xxclouddd/eigen,artsy/eigen,ashkan18/eigen,TribeMedia/eigen,orta/eigen,ichu501/eigen,ichu501/eigen,xxclouddd/eigen,srrvnn/eigen,ACChe/eigen,orta/eigen,zhuzhengwei/eigen,foxsofter/eigen,xxclouddd/eigen,neonichu/eigen,xxclouddd/eigen,zhuzhengwei/eigen,ayunav/eigen,gaurav1981/eigen,Havi4/eigen,Havi4/eigen,Havi4/eigen,srrvnn/eigen,ppamorim/eigen,1aurabrown/eigen,zhuzhengwei/eigen,mbogh/eigen,Shawn-WangDapeng/eigen,srrvnn/eigen,srrvnn/eigen,TribeMedia/eigen,liduanw/eigen,liduanw/eigen,xxclouddd/eigen,neonichu/eigen,foxsofter/eigen,ichu501/eigen,orta/eigen,ppamorim/eigen,neonichu/eigen,Havi4/eigen,artsy/eigen,ppamorim/eigen,liduanw/eigen,TribeMedia/eigen