Unify versions used in integration tests

This commit makes sure the integration tests use the same versions as
the one managed by `spring-boot-dependencies` (including Maven plugins).

Closes gh-8947

spring-boot-tools/spring-boot-maven-plugin/src/it/module/pom.xml

@@ -28,7 +28,7 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-jar-plugin</artifactId>
-				<version>2.4</version>
+				<version>@maven-jar-plugin.version@</version>
 			</plugin>
 		</plugins>
 	</build>