[Doc] Remove reference to UNIX sockets in StreamPeer.
[Doc] Remove reference to UNIX sockets in StreamPeer.

That class can be used as a base to implement them, but there is no
actual implementation for it in Godot.

(cherry picked from commit e858f7c2ead49cee8689fc03546e6f505f0fd17a)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot