feat: using a more precise return

[warcooft]

Description

The previous behavior may look like there is no problem, but when the user submits the verification code it will automatically change the state of the URL to http://localhost:8080/auth/a/verify.

When the codes don't match and they accidentally refresh the page it will cause a 404 error because the route auth/a/verify with the GET method does not exist.

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]

Please write test code to prove your code works fine in all PRs.
See https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/pull_request.md#unit-testing

[kenjis]

The following test fails. Please fix your code. Thank you.

There was 1 failure:

1) Tests\Controllers\RegisterTest::testRegisterActionRedirectsIfTokenNotMatch
Do not see 'The code was incorrect.' in response.
Failed asserting that false is true.

/home/runner/work/shield/shield/vendor/codeigniter4/framework/system/Test/TestResponse.php:436
/home/runner/work/shield/shield/tests/Controllers/RegisterTest.php:360
phpvfscomposer:///home/runner/work/shield/shield/vendor/phpunit/phpunit/phpunit:97

https://github.com/codeigniter4/shield/actions/runs/9990325709/job/27721717998?pr=1146