Drop Puppet 5 support

[ehelms]

No description provided.

[ekohl]

This bit was only needed until SERVER-2597 was fixed. That was part of Puppetserver 6.10.0 which we can pretty much assume if 6.15.0 is the minimal version. In theory the server could be older, but I don't think we need to support that.

puppet-foreman/lib/puppet/functions/foreman/enc.rb

Lines 48 to 54 in 6c902a4

	# Puppetserver doesn't implement HTTP auth on get requests
	# https://tickets.puppetlabs.com/browse/SERVER-2597
	if defined?(Puppet::Server::HttpClient) && conn.is_a?(Puppet::Server::HttpClient) && options[:basic_auth]
	require 'base64'
	encoded = Base64.strict_encode64("#{options[:basic_auth][:user]}:#{options[:basic_auth][:password]}")
	headers["Authorization"] = "Basic #{encoded}"
	end

It can be dropped since the basic auth option is passed correctly in the request.