Fix typo in CONTRIBUTING.md
Fix typo in CONTRIBUTING.md

ocadotechnology/calico,anortef/calico,matthewdupre/felix,ocadotechnology/calico,kasisnu/calico,neiljerram/felix,neiljerram/felix,Metaswitch/calico,TrimBiggs/calico,beddari/calico,alexhersh/calico,anortef/calico,Metaswitch/calico,TrimBiggs/calico,matthewdupre/felix,kasisnu/calico,beddari/calico,neiljerram/felix,neiljerram/felix,alexhersh/calico