Fix createFromInterface return type

[VincentLanglet]

See:

• https://github.com/php/php-src/blob/e48099a03c677bea5d0c615cefcab094f8b5253b/ext/date/php_date.stub.php#L361-L362
• https://github.com/php/php-src/blob/e48099a03c677bea5d0c615cefcab094f8b5253b/ext/date/php_date.stub.php#L564-L565

[VincentLanglet]

How do I avoid the test failure @isfedorov @LolGleb ?

Because as you can see in php-src there is a different return type in phpdoc and native type
with a // TODO return type should be static.

[LolGleb]

Hi, thanks for the PR. As far as I can tell, your changes look good. We'll need some time on our end to figure out how to adapt the tests, which will take a while.

If you'd like to help with that, we'd be super grateful, but just a heads-up, framework is quite complex