Restore strict_types enforcement in php-cs-fixer config

php-cs-fixer v3.95.0 added a `strategy` option to `declare_strict_types`
and set `@Symfony:risky` to `'strategy' => 'remove'` (see
PHP-CS-Fixer/PHP-CS-Fixer#9384), which causes the
preset we inherit to strip `declare(strict_types=1);` from every file on
the next CI run. Override with `'strategy' => 'enforce'` to keep the
pre-v3.95 behavior — strict types stay declared.

Closes STF-223.

Author: oschwald

.php-cs-fixer.php

@@ -15,6 +15,7 @@
         'array_syntax' => ['syntax' => 'short'],
         'combine_consecutive_unsets' => true,
         'concat_space' => [ 'spacing' => 'one'],
+        'declare_strict_types' => true,
         'explicit_string_variable' => false,
         'fopen_flags' => ['b_mode' => true],
         'heredoc_to_nowdoc' => true,