[COOK-1087] Update the CONTRIBUTING file to fix a minor typo
[COOK-1087] Update the CONTRIBUTING file to fix a minor typo

Altiscale/iptables,gene1wood/iptables,som3guy/iptables,som3guy/iptables,gt28/jtu_test,NREL-cookbooks/iptables,patcon/iptables,czeeb/iptables,alexdglover/iptables,cookbooks/oc-iptables,NREL-cookbooks/iptables,matschaffer/iptables,mjmeintjes/iptables,grengojbo/iptables,ashumski/iptables,kangaechu/iptables,hw-cookbooks/iptables,opscode-cookbooks/iptables,som3guy/iptables,czeeb/iptables,deathsyn/iptables-osa,chef-cookbooks/iptables,patcon/iptables,patcon/iptables,gt28/jtu_test,ashumski/iptables,opscode-cookbooks/iptables,ashumski/iptables,czeeb/iptables,opscode-cookbooks/iptables,NREL-cookbooks/iptables,Altiscale/iptables,chef-cookbooks/iptables,RSEmail/iptables,phlipper/iptables,apptentive/iptables,gt28/jtu_test,damienmg/iptables,Altiscale/iptables,jeffrafter/iptables,NREL-cookbooks/iptables,dldinternet/iptables,chef-cookbooks/iptables,jmanero/iptables