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

opscode-cookbooks/heartbeat,stem/heartbeat,cla-rce/heartbeat,stem/heartbeat,cla-rce/heartbeat,chef-cookbooks/heartbeat,revinate/heartbeat,chef-cookbooks/heartbeat,cookbooks/oc-heartbeat,opscode-cookbooks/heartbeat