Modified AdditionalAuthenticationProviders field in GraphQlApi to be a list (#1479)
Modified AdditionalAuthenticationProviders field in GraphQlApi to be a list (#1479)

* Modified AdditionalAuthenticationProviders field in GraphQlApi to be a list
* Updated naming convention for AdditionalAuthenticationProvider, which is now contained within a list
cloudtools/troposphere,ikben/troposphere,cloudtools/troposphere,ikben/troposphere