Remove redundant Rspec settings from spec_helper.rb

As part of MODULES-4976 I was investigating the use of the following code snippet:

  if Puppet::Util::Platform.windows?

    config.output_stream = $stdout

    config.error_stream = $stderr

    config.formatters.each { |f| f.instance_variable_set(:@output, $stdout) }

  end

I noticed that this still exists in Puppet at;
https://github.com/puppetlabs/puppet/blob/master/spec/spec_helper.rb#L87-L96

This code was originally to get around an issue with the win32_console gem back in the Ruby 1.x days.

https://github.com/puppetlabs/puppet/commit/4ffc02d22093f0b76046a51eee603932a9b14f62
and
https://github.com/puppetlabs/puppet/commit/0babce626adb2e59bf212e4272b9e088a7b559a7

As Puppet 3 is now end of life, Ruby 2.x no longer uses the win32_console gem, this code is no longer required to run specs on Windows correctly.

This ticket is track removing this from the the spec_helper