Fix SOCKS support for 'http://' URLs

[lovelydinosaur]

Closes#491

The SOCKS proxy code was missing the check for "is this an https URL or not" at the point of setting up SSL with the remote endpoint.

Compare this...

httpcore/httpcore/_async/socks_proxy.py

Lines 241 to 257 in 25a5ad3

	# Upgrade the stream to SSL
	ssl_context= (
	default_ssl_context()
	ifself._ssl_contextisNone
	elseself._ssl_context
	)
	alpn_protocols= ["http/1.1", "h2"] ifself._http2else ["http/1.1"]
	ssl_context.set_alpn_protocols(alpn_protocols)
	kwargs= {
	"ssl_context": ssl_context,
	"server_hostname": self._remote_origin.host.decode("ascii"),
	"timeout": timeout,
	}
	asyncwithTrace("connection.start_tls", request, kwargs) astrace:
	stream=awaitstream.start_tls(**kwargs)
	trace.return_value=stream

To the equivalent within a regular connection...

httpcore/httpcore/_async/connection.py

Lines 135 to 151 in 25a5ad3

	ifself._origin.scheme==b"https":
	ssl_context= (
	default_ssl_context()
	ifself._ssl_contextisNone
	elseself._ssl_context
	)
	alpn_protocols= ["http/1.1", "h2"] ifself._http2else ["http/1.1"]
	ssl_context.set_alpn_protocols(alpn_protocols)
	kwargs= {
	"ssl_context": ssl_context,
	"server_hostname": self._origin.host.decode("ascii"),
	"timeout": timeout,
	}
	asyncwithTrace("connection.start_tls", request, kwargs) astrace:
	stream=awaitstream.start_tls(**kwargs)
	trace.return_value=stream

Bit silly really. Fix is easy-peasy.