Upgraded TestNG dependency for examples

Address CVE in TestNG

Author: jlouvel

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

@@ -22,7 +22,7 @@
         <dependency>
             <groupId>org.testng</groupId>
             <artifactId>testng</artifactId>
-            <version>7.0.0</version>
+            <version>7.5.1</version>
         </dependency>
         <dependency>
             <groupId>org.restlet</groupId>

org.restlet.java/org.restlet/src/main/java/org/restlet/service/LogService.java

@@ -11,7 +11,6 @@
 
 import java.util.logging.Level;
 
-import org.restlet.Application;
 import org.restlet.Context;
 import org.restlet.Request;
 import org.restlet.Response;