refactor: fix Security test fail by itself

[paulbalandan]

Description
Running SecurityTest by itself leads to failures, which means it is not isolated enough and dependent on other tests.

❯ vendor/bin/phpunit --filter SecurityTest
PHPUnit 11.5.55 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.5.3 with Xdebug 3.5.1
Configuration: /Users/paul/Workspace/CodeIgniter4/phpunit.xml.dist

........E.E.E......FFF.......                                                                                                       29 / 29 (100%)

Time: 00:02.360, Memory: 82.00 MB

There were 3 errors:

1) CodeIgniter\Security\SecurityTest::testCSRFVerifyHeaderReturnsSelfOnMatch
CodeIgniter\Security\Exceptions\SecurityException: The action you requested is not allowed.

/Users/paul/Workspace/CodeIgniter4/system/Security/Security.php:263
/Users/paul/Workspace/CodeIgniter4/tests/system/Security/SecurityTest.php:170

2) CodeIgniter\Security\SecurityTest::testCSRFVerifyJsonReturnsSelfOnMatch
CodeIgniter\Security\Exceptions\SecurityException: The action you requested is not allowed.

/Users/paul/Workspace/CodeIgniter4/system/Security/Security.php:263
/Users/paul/Workspace/CodeIgniter4/tests/system/Security/SecurityTest.php:206

3) CodeIgniter\Security\SecurityTest::testCSRFVerifyPutBodyReturnsSelfOnMatch
CodeIgniter\Security\Exceptions\SecurityException: The action you requested is not allowed.

/Users/paul/Workspace/CodeIgniter4/system/Security/Security.php:263
/Users/paul/Workspace/CodeIgniter4/tests/system/Security/SecurityTest.php:242

--

There were 3 failures:

1) CodeIgniter\Security\SecurityTest::testGetPostedTokenReturnsTokenFromHeader
Failed asserting that null is identical to '8b9218a55906f9dcc1dc263dce7f005a'.

/Users/paul/Workspace/CodeIgniter4/tests/system/Security/SecurityTest.php:346

2) CodeIgniter\Security\SecurityTest::testGetPostedTokenReturnsTokenFromJsonBody
Failed asserting that null is identical to '8b9218a55906f9dcc1dc263dce7f005a'.

/Users/paul/Workspace/CodeIgniter4/tests/system/Security/SecurityTest.php:355

3) CodeIgniter\Security\SecurityTest::testGetPostedTokenReturnsTokenFromFormBody
Failed asserting that null is identical to '8b9218a55906f9dcc1dc263dce7f005a'.

/Users/paul/Workspace/CodeIgniter4/tests/system/Security/SecurityTest.php:364

ERRORS!
Tests: 29, Assertions: 34, Errors: 3, Failures: 3.

Generating code coverage report in Clover XML format ... done [00:00.463]

Generating code coverage report in HTML format ... done [00:03.204]

Ref: #9968

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide