curl_multi_init may return false (like curl_init)

[InvisibleSmiley]

From manual page: https://php.net/function.curl-multi-init

---

https://www.php.net/manual/en/function.curl-multi-init.php#refsect1-function.curl-multi-init-returnvalues
states that the result can be false

https://www.php.net/manual/en/function.curl-multi-init.php#refsect1-function.curl-multi-init-description
does not reflect that

PHPStan seems to rely on the latter definition.

For comparison, here Description and Return Values match:
https://www.php.net/manual/en/function.curl-init.php

[InvisibleSmiley]

Note: If it's the other way around, the documentation still needs updating. ;)

[othercorey]

Looks like the return description is wrong:

https://github.com/php/php-src/blob/master/ext/curl/multi.c#L60

[Girgias]

Fixed by: #2591