Add @Override to remaining source files

Issue: SPR-10130

spring-jdbc/src/test/java/org/springframework/jdbc/Customer.java

@@ -43,6 +43,7 @@ public class Customer {
 	}
 
 
+	@Override
 	public String toString() {
 		return "Customer: id=" + id + "; forename=" + forename;
 	}

spring-jdbc/src/test/java/org/springframework/jdbc/core/RowMapperTests.java

@@ -50,6 +50,7 @@ public class RowMapperTests extends TestCase {
 
 	private List<TestBean> result;
 
+	@Override
 	@Before
 	public void setUp() throws SQLException {
 		connection = mock(Connection.class);