NH-3408 - Fix mapping for non MS SQL Server dialects

Author: hazzik

src/NHibernate.Test/NHSpecificTest/NH3408/Mappings.hbm.xml

@@ -11,9 +11,9 @@
     <set name="NationalHolidays" table="Holiday">
       <key column="CalendarID" />
       <element type="System.DateTime">
-        <column name="Holiday" sql-type="smalldatetime" />
+        <column name="Holiday" />
       </element>
     </set>
   </class>
 
-</hibernate-mapping>
+</hibernate-mapping>