removed checks of not existing class Zend\Math\BigInteger

[marc-mabe]

This addresses the last note of #3512
The second note seems to be fixed already

but the first one is already there and I cant fix:

#grep -iHrn 'ConstraintKeyObject' library/Zend/Db/
../library/Zend/Db/Metadata/Source/AbstractSource.php:398:                $keys[] = $key = new Object\ConstraintKeyObject($constraintKeyInfo['column_name']);

@ralphschindler @Maks3w ping

[Maks3w]

Why do you remove this?

BigInteger feature is not removed. Just the old deprecated message

[marc-mabe]

If the class doesn't exist it's not possible to get this as PHP type