Fix deprecation warnings in PHP 8.4

[jaumarar]

Hi again, long time no see. Using this package in PHP 8.4 gives me this warn:

Deprecated: PhpDevCommunity\DotEnv::__construct(): Implicitly marking parameter $processors as nullable is deprecated, the explicit nullable type must be used instead in /var/www/api/vendor/phpdevcommunity/php-dotenv/src/DotEnv.php on line 29

Deprecated: PhpDevCommunity\DotEnv::setProcessors(): Implicitly marking parameter $processors as nullable is deprecated, the explicit nullable type must be used instead in /var/www/api/vendor/phpdevcommunity/php-dotenv/src/DotEnv.php on line 69

[michelphp]

I've created the 3.0.1 tag to this fix.