Read from reverse_proxy_addresses not reverse_proxies

Problem/Motivation

The constructor of the Drupal\acquia_purge\AcquiaCloud\PlatformInfo class reads from a setting called reverse_proxies. But it is actually reverse_proxy_addresses. This isn't a D7-ism either, the value was always the same name. For finding and reporting the issue, the credit goes to Matt Glaman.

Steps to reproduce

1. In your settings.php file uncomment these lines:
   
   $settings['reverse_proxy'] = TRUE;

$settings['reverse_proxy_addresses'] = ['a.b.c.d', 'e.f.g.h/24'];
2. In your debugger set a breakpoint at \Drupal\acquia_purge\AcquiaCloud\PlatformInfo::__construct()
3. On the /admin/config/development/performance/purge page try to add an „Acquia Cloud” type of purger plugin
4. The debugger shows that variable reverse_proxies does not get a value which is bad:
   

Proposed resolution

Fix the naming mistake when reading from site settings.

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes

None.