move the tst test_http_response_code_constants from http.php to getStatusHeaderDesc.php

[pbearne]

Let's get all tests into the same file

Moves test_http_response_code_constants() from the HTTP API test file into the test class for get_status_header_desc(), so all tests for that function live in one place.

What the problem was:

• test_http_response_code_constants() exercises get_status_header_desc() but was located in tests/phpunit/tests/http/http.php (Tests_HTTP_HTTP).

What the fix does:

• Moves the test method into Tests_Functions_GetStatusHeaderDesc (tests/phpunit/tests/functions/getStatusHeaderDesc.php).
• Drops the redundant method-level @covers ::get_status_header_desc, as the class-level docblock already declares it.

Approach and why:

• Test body is unchanged; this only relocates it to the canonical file for the function under test, improving discoverability and grouping.

Trac ticket: https://core.trac.wordpress.org/ticket/65527

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Used for: Ticket analysis and tests. All changes were reviewed, validated against the codebase, and are taken responsibility for by me.