[Docs] [HTTP] [Trusted proxies] Removed note about adding 127.0.0.1

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3+ (applies to 2.2 too but wasn't stated in the 2.2 docs anyway)
| Fixed tickets | none

Removed the note about the need to add 127.0.0.1 to the list of trusted proxies when using Symfony's reversed proxy.

I don't think that adding ```127.0.0.1``` to the list of trusted proxies is needed. The only place where Symfony uses the list of trusted proxies is in the ```FragmentListener``` (https://github.com/symfony/symfony/blob/2.3/src/Symfony/Component/HttpKernel/EventListener/FragmentListener.php#L81) and there they are merged with the result of ```FragmentListener#getLocalIpAddresses()``` (https://github.com/symfony/symfony/blob/2.3/src/Symfony/Component/HttpKernel/EventListener/FragmentListener.php#L96) which already returns ```127.0.0.1``` among the list of locally (and thus trusted) ips.