QueryHintSQLServer2012Test is wrong

1. the test uses an incorrect entity-name when querying the Employee entity
2. SQL server doesn't have a USE_CONCAT hint. We can use 'CONCAT UNION' instead, for example
3. This line doesn't even deserve a comment........ https://github.com/hibernate/hibernate-orm/blob/bd256e4783219f4a765219cf625bb658fcb5fde1/hibernate-core/src/test/java/org/hibernate/test/queryhint/QueryHintSQLServer2012Test.java#L115