remove cause of unreachable code/dead code. Not necessary because carto redis assures at least the default api key

lib/cartodb/api/auth_api.js

@@ -86,8 +86,6 @@ AuthApi.prototype.authorizedByAPIKey = function(user, res, callback) {
         }
 
         if ( !isValidApiKey(apikey)) {
-            return callback(null, true); // AUTH_FALLBACK :S If api key not found, use default_public
-
             const error = new Error('Unauthorized');
             error.type = 'auth';
             error.subtype = 'api-key-not-found';