Change the exclude syntax at pom.

Author: Aleksi Salmela

pom.xml

@@ -90,9 +90,7 @@
                 <artifactId>maven-surefire-plugin</artifactId>
                 <version>2.18.1</version>
                 <configuration>
-                    <excludes>
-                        <exclude>**/dummy-courses/**/*</exclude>
-                    </excludes>
+                    <excludes>**/dummy-courses/**/*</excludes>
                 </configuration>
             </plugin>
             <plugin>