fix(opcache): remove leftover opcache.ini for PHP >= 8.5

[potsky]

Context

OPCache became a required, statically-built extension in PHP 8.5 (opcache-required RFC), so it can no longer be loaded as an external Zend extension and the shared opcache.so file is no longer shipped.

support/package_php was already updated in bcc5875 to stop writing etc/conf.d/opcache.ini when packaging PHP >= 8.5.

However, PHP 8.5 binaries packaged before that fix still contain the
obsolete file, and they remain the ones currently served to apps using
PHP 8.5.x on scalingo-22 (the 8.5.6 build for no-debug-non-zts-20250925
fetched from the Swift bucket).

Symptom

Every PHP invocation during build and runtime emits:

PHP Warning:  Failed loading Zend extension 'opcache.so'
(tried: /app/vendor/php/lib/php/extensions/no-debug-non-zts-20250925/opcache.so
(/app/vendor/php/lib/php/extensions/no-debug-non-zts-20250925/opcache.so: cannot open shared object file: No such file or directory),
/app/vendor/php/lib/php/extensions/no-debug-non-zts-20250925/opcache.so.so
(/app/vendor/php/lib/php/extensions/no-debug-non-zts-20250925/opcache.so.so: cannot open shared object file: No such file or directory))
in Unknown on line 0

This appears for every:

• composer install invocation (post-install scripts, package:discover, etc.)
• php artisan call during build
• Horizon worker startup
• Scheduler tick
• scalingo run php -m (which still correctly reports Zend OPcache as built-in)

OPCache itself is active (built into the binary), so there is no runtime
impact — but the warning pollutes every log line.

Fix

Remove ${VENDORED_PHP}/etc/conf.d/opcache.ini defensively in bin/compile
when PHP >= 8.5, immediately after fetch_engine_package php and after
sourcing .profile.d/php.sh (so php_api_version() and
PHP_MODULE_API_VERSIONS are both available).

This works regardless of whether the downloaded PHP binary was packaged
before or after bcc5875, and is a no-op once the PHP 8.5 binary is
re-released without the file. Behavior for PHP < 8.5 is unchanged.

Reproduction

Any app declaring "php": "8.5.*" in composer.json on scalingo-22
reproduces the warning during build and runtime.

Test

Bash syntax checked locally with bash -n bin/compile.

[Frzk]

LGTM, thanks a lot @potsky <3