Aligned TestNG and MongoDB dependency versions

Author: jlouvel

org.restlet.java/org.restlet.example/pom.xml

@@ -17,12 +17,12 @@
         <dependency>
             <groupId>org.mongodb</groupId>
             <artifactId>mongo-java-driver</artifactId>
-            <version>2.11.3</version>
+            <version>${lib-mongodb-version}</version>
         </dependency>
         <dependency>
             <groupId>org.testng</groupId>
             <artifactId>testng</artifactId>
-            <version>7.5.1</version>
+            <version>${lib-testng-version}</version>
         </dependency>
         <dependency>
             <groupId>org.restlet</groupId>