Update CONTRIBUTING.md
Update CONTRIBUTING.md

Just replaced Jarba's by Jarbas', as the original name already have 's' in the end.
wisner23/serenata-de-amor,marcusrehm/serenata-de-amor,marcusrehm/serenata-de-amor,marcusrehm/serenata-de-amor,marcusrehm/serenata-de-amor,wisner23/serenata-de-amor,datasciencebr/serenata-de-amor,datasciencebr/serenata-de-amor