Fix name of REST API guide to match title
Fixes nav title to match actual title of page: https://docs.gitlab.com/ee/development/documentation/restful_api_styleguide.html
Related issue: gitlab#396567 (closed)
Fixes nav title to match actual title of page: https://docs.gitlab.com/ee/development/documentation/restful_api_styleguide.html
Related issue: gitlab#396567 (closed)