Remove workaround for old HTTP.jl version?

[BioTurboNick]

AWS.jl/src/utilities/request.jl

Lines 215 to 234 in c16fb18

	get_response = function ()
	# Use a sacrificial I/O stream so that we only write to the `response_stream`
	# once even with multiple attempted requests. Additionally this works around the
	# HTTP.jl issue (https://github.com/JuliaWeb/HTTP.jl/issues/543) where the
	# `response_stream` is closed automatically. Effectively, this works as if we're
	# not using streaming I/O at all, as we write all data at once, but only
	# returning data via I/O ensures we aren't relying on response's body being
	# populated.
	buffer = Base.BufferStream()
	response = @mock HTTP.request(
	request.request_method,
	HTTP.URI(request.url),
	HTTP.mkheaders(request.headers),
	request.content;
	redirect=false,
	retry=false,
	response_stream=buffer,
	http_options...,
	)

Noticed this appears to be a leftover from pre-v1 HTTP.jl behavior.