Remove hibernate-entitymanager.version property

Users that wish to override the version of Hibernate need to override
the hibernate.version property, as it’s the one used when declaring the
dependency management for Hibernate’s modules, so the
hibernate-entitymanager.version property is of little value.

Closes gh-3004

spring-boot-dependencies/pom.xml

@@ -75,7 +75,6 @@
 		<hamcrest.version>1.3</hamcrest.version>
 		<hazelcast.version>3.4.2</hazelcast.version>
 		<hibernate.version>4.3.10.Final</hibernate.version>
-		<hibernate-entitymanager.version>${hibernate.version}</hibernate-entitymanager.version>
 		<hibernate-validator.version>5.1.3.Final</hibernate-validator.version>
 		<hikaricp.version>2.3.7</hikaricp.version>
 		<hornetq.version>2.4.7.Final</hornetq.version>