MongoServer.Create has already created 100 servers which is the maximum number of servers allowed.
Such error occurs because of internal limit of 100 Server instance in MongoDb driver. If you have many connections then MongoServer.Create API is called too many times during validation phase and you may see such errors.
Try to set Delayvalidation=True for Data Flow task to avoid such error.
Goto Control Flow > Right Click on Data Flow task > Click Properties
In the Property Grid make sure DelayValidation is set to True