remove unused field from Subject struct
remove unused field from Subject struct

The whitelisting of fields was replaced by a policy-level CSR whitelist with https://github.com/cloudflare/cfssl/commit/a05c5d2970952662f538c2dc15a6933b19d6566c

bifurcation/cfssl,letsencrypt/cfssl,mitchcapper/cfssl,wl2002/cfssl,haneric21/cfssl,drcapulet/cfssl,cloudflare/cfssl,dhiltgen/cfssl,APTy/cfssl,gtank/cfssl,cloudflare/cfssl,dhiltgen/cfssl,sfurman3/cfssl,bossjones/cfssl,j-delaney/cfssl,terinjokes/cfssl,bossjones/cfssl,jmhodges/cfssl,drcapulet/cfssl,endocode/cfssl,endocode/cfssl,cloudflare/cfssl,dhiltgen/cfssl,terinjokes/cfssl,haneric21/cfssl,bossjones/cfssl,APTy/cfssl,rolandshoemaker/cfssl,mclem/cfssl,sfurman3/cfssl,mclem/cfssl,mitchcapper/cfssl,bifurcation/cfssl,dhiltgen/cfssl,geligaoli/cfssl,drcapulet/cfssl,thesamet/cfssl,rolandshoemaker/cfssl,sdgdsffdsfff/cfssl,endocode/cfssl,sdgdsffdsfff/cfssl,BugRoger/cfssl,rolandshoemaker/cfssl,letsencrypt/cfssl,gtank/cfssl,APTy/cfssl,sfurman3/cfssl,geligaoli/cfssl,endocode/cfssl,jmhodges/cfssl,jmhodges/cfssl,BugRoger/cfssl,bifurcation/cfssl,endocode/cfssl,thesamet/cfssl,letsencrypt/cfssl,codyli520/cfssl,sfurman3/cfssl,mitchcapper/cfssl,geligaoli/cfssl,j-delaney/cfssl,sdgdsffdsfff/cfssl,sfurman3/cfssl,mclem/cfssl,codyli520/cfssl,wl2002/cfssl,terinjokes/cfssl,BugRoger/cfssl,thesamet/cfssl,haneric21/cfssl,haneric21/cfssl,letsencrypt/cfssl,mclem/cfssl,geligaoli/cfssl,drcapulet/cfssl,sdgdsffdsfff/cfssl,haneric21/cfssl,gtank/cfssl,terinjokes/cfssl,wl2002/cfssl,codyli520/cfssl,APTy/cfssl,j-delaney/cfssl,APTy/cfssl,thesamet/cfssl,BugRoger/cfssl,dhiltgen/cfssl,bossjones/cfssl,codyli520/cfssl,j-delaney/cfssl,wl2002/cfssl,j-delaney/cfssl,wl2002/cfssl,bifurcation/cfssl,rolandshoemaker/cfssl,geligaoli/cfssl,codyli520/cfssl,drcapulet/cfssl,rolandshoemaker/cfssl,gtank/cfssl,jmhodges/cfssl,mclem/cfssl,cloudflare/cfssl