Update CONTRIBUTING.md (#585)
Update CONTRIBUTING.md (#585)

Fixing typo for terraform
GoogleCloudPlatform/professional-services,GoogleCloudPlatform/professional-services,GoogleCloudPlatform/professional-services,GoogleCloudPlatform/professional-services,GoogleCloudPlatform/professional-services,GoogleCloudPlatform/professional-services,GoogleCloudPlatform/professional-services,GoogleCloudPlatform/professional-services,GoogleCloudPlatform/professional-services