cleanup: remove phpcheck.php diagnostic script

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

phpcheck.php

@@ -1,7 +0,0 @@
-<?php
-echo "PHP versio: " . PHP_VERSION . "\n";
-echo "PDO loaded: " . (extension_loaded('pdo') ? 'KYLLÄ' : 'EI') . "\n";
-echo "PDO MySQL: " . (extension_loaded('pdo_mysql') ? 'KYLLÄ' : 'EI') . "\n";
-echo "MySQLi: " . (extension_loaded('mysqli') ? 'KYLLÄ' : 'EI') . "\n";
-echo "\nLadatut laajennukset:\n";
-echo implode(', ', get_loaded_extensions());