Fix LiveViewListener for LiveView < v0.16

[mcrumm]

LiveViewListener uses the transport (socket) pid from the ToolbarLive socket in its pattern match for telemetry events. We do this because we want the toolbar to receive events only from the LiveView it is profiling.

LiveView v0.16+ stores the transport_pid on the Socket struct, but prior to that we need to use LiveView.transport_pid/1 on a connected socket.