[php-src] Issue #21795: ext/curl/tests/bug71523 should be online test

Issue: https://github.com/php/php-src/issues/21795
Author: mixen56

### Description

Please, add `SKIP_ONLINE_TESTS` to test `ext/curl/tests/bug71523.phpt`.
In my case test fails if:
- `resolv.conf` is configured
- but there is no `http_proxy` env variable (my computer is connected to the network via a proxy)

I think this issue may not require reproduction because the test tries connect to google.com.
So, logically, test should be marked as online.
Now in master (https://github.com/php/php-src/blob/master/ext/curl/tests/bug71523.phpt) this test is not marked as online.

### PHP Version

```plain
master
```

### Operating System

_No response_