Changes to GET /v1/:parent/ctas

removed the media type */* for the response with the status 200

the security scope https://www.googleapis.com/auth/webcontentpublisher.publications.manage.system was added to the endpoint's security scheme Oauth2

the security scope https://www.googleapis.com/auth/webcontentpublisher.publications.manage.system was added to the endpoint's security scheme Oauth2c

the security scope https://www.googleapis.com/auth/subscribewithgoogle.publications.entitlements.readonly was removed from the endpoint's security scheme Oauth2

the security scope https://www.googleapis.com/auth/subscribewithgoogle.publications.entitlements.readonly was removed from the endpoint's security scheme Oauth2c

added the optional property ctas/items/newsletterConfig/optInRequired to the response with the 200 status