getAlias() must be typed string

[knarficious]

Since Symfony 6.0 "Declaration of Msalsas\GdprConsentBannerBundle\DependencyInjection\MsalsasGdprConsentBannerExtension::getAlias() must be compatible with Symfony\Component\DependencyInjection\Extension\Extension::getAlias(): string"

public function getAlias():string{ return 'msalsas_gdpr_consent_banner'; }