Fix dependencies (eclipse-che#5590)

Signed-off-by: Vitalii Parfonov <vparfonov@redhat.com>

Author: vparfonov

plugins/plugin-help/che-plugin-help-ext-client/pom.xml

@@ -34,6 +34,10 @@
             <groupId>javax.inject</groupId>
             <artifactId>javax.inject</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.eclipse.che.core</groupId>
+            <artifactId>che-core-commons-gwt</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.eclipse.che.core</groupId>
             <artifactId>che-core-ide-api</artifactId>