refactor: remove unused non-empty array in RequestTrait

[paulbalandan]

Description
Brought by RemoveUnusedNonEmptyArrayBeforeForeachRector but manually made as I cannot use rector on Windows.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[kenjis]

The $proxyIPs value may be an empty string if Config\App is not updated.

CodeIgniter4/app/Config/App.php

Lines 341 to 346 in 9d95248

	* Comma-separated: '10.0.1.200,192.168.5.0/24'
	* Array: ['10.0.1.200', '192.168.5.0/24']
	*
	* @var string|string[]
	*/
	public $proxyIPs = '';

In this case, this change causes:

ErrorException
foreach() argument must be of type array|object, string given
SYSTEMPATH/HTTP/RequestTrait.php at line 82

[paulbalandan]

Ok. Judging by how $this->proxyIPs is injected with value, L68 should be revised to check that $proxyIPs should be an array even if empty or not.

[kenjis]

It is better to set [] if $proxyIPs = ''. Many devs do not use Proxy at all.

Or add "$proxyIPs must be an array" to Mandatory File Changes in the upgrade guide.

[kenjis]

I sent another PR #7620
and will make sure $proxyIPs is an array in 4.4. See #7621