Outdated references to OpenSSL / MbedTLS

[ericphanson]

HTTP.jl/src/HTTP.jl

Lines 193 to 194 in 10182c0

	- `socket_type_tls = MbedTLS.SSLContext`, the type of socket to use for TLS connections. Defaults to `MbedTLS.SSLContext`.
	Also supported is passing `socket_type_tls = OpenSSL.SSLStream`. To change the global default, set `HTTP.SOCKET_TYPE_TLS[] = OpenSSL.SSLStream`.

since #1039 changed the default to OpenSSL

[quinnj]

will be fixed in #1079