Update building_application.md

[Joseandresc]

Changed "new connection" to "new Connection" in

var connection = new Connection(
    new Address("amqps://contoso.com:5671"),
    SaslProfile.Anonymous,
    new Open() { ContainerId = "client.1.2", HostName = "contoso.com", MaxFrameSize = 8 * 1024 },
    (c, o) => { /* do someting with remote Open o */ });