fix IntlDateFormatter::create return signature

[Kleinast]

Conf php doc => https://www.php.net/manual/en/intldateformatter.create.php

I didn't manage to install and run test for this phpstan-src project.
When I do:

composer install
make tests

I get

php vendor/bin/paratest --runner WrapperRunner --no-coverage
You need to set up the project dependencies using the following commands:
curl -s http://getcomposer.org/installer | php
php composer.phar install

autoload.php is not created
and if I do:
composer update
it endup with

- Applying patches for jetbrains/phpstorm-stubs (2)
    ~ phpstan/phpstan-src: patches/PDO.patch [NEW]
      Failed to apply the patch. Halting execution!

Did I miss something to make it work ?

Thx for your time

[ondrejmirtes]

Thank you!

[ondrejmirtes]

About your issues - I don't know, it's pretty much standard, it works on my machine and in CI. What error did you get with composer install?