Remove unused Http proxy class

[mikkamp]

Changes proposed in this Pull Request:

The Http proxy class was initially added in PR #69 with the comment:

A Proxy for making HTTP requests to the connect server in the future.

In the end we decided to go with a Guzzle client to send requests to the connect server. So in the interest of reducing code this PR removes this class. If we change our mind this PR can be reverted to bring it back.

Detailed test instructions:

1. Run some basic smoke tests to confirm API requests continue to work.
2. Run unit tests to confirm they all pass.

Changelog entry

• Tweak - Remove unused Http proxy class.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.1%. Comparing base (c8c1efa) to head (105ce3b).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##             develop   #2763     +/-   ##
===========================================
+ Coverage       67.0%   67.1%   +0.1%     
+ Complexity      4692    4687      -5     
===========================================
  Files            480     479      -1     
  Lines          19601   19586     -15     
===========================================
  Hits           13141   13141             
+ Misses          6460    6445     -15     

Flag	Coverage Δ
php-unit-tests	67.1% <ø> (+0.1%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...rnal/DependencyManagement/ProxyServiceProvider.php	0.0% <ø> (ø)

[puntope]

Thanks @mikkamp LGTM ✅

• Tested there is no more Proxies\Http usage. Now I can only see Guzzle\Http and Psr\Http
• Tested a full onboarding
• Tested updating Shipping settings
• Checked for fatals or warnings in logs