Fix wrong type in phpdoc of AbstractIdGenerator
Fix wrong type in phpdoc of AbstractIdGenerator

\Doctrine\ORM\Mapping\Entity is the annotation class which is not correct. The entity object itself is meant here as tests also assume see https://github.com/doctrine/doctrine2/blob/2.6/tests/Doctrine/Tests/ORM/Id/AssignedGeneratorTest.php#L28

Found this when running phpstan on our code that used a custom generator.
doctrine/doctrine2,Ocramius/doctrine2,bigfoot90/doctrine2,Ocramius/doctrine2,Ocramius/doctrine2,Sitetheory/doctrine2,bigfoot90/doctrine2,doctrine/doctrine2,Sitetheory/doctrine2