chore(user-guide/testing): Add assertj to Matrix

Related-to: camunda/camunda-bpm-platform#4273

Author: psavidis

content/user-guide/testing/_index.md

@@ -411,6 +411,12 @@ With Camunda 7.17.0 the project was moved into the [Camunda 7 repository](https:
     <td>7.20.0<br/>7.21.0</td>
     <td>7.20.0<br/>7.21.0</td>
   </tr>
+  <tr>
+    <td>camunda-bpm-assert</td>
+    <td>3.25.3</td>
+    <td>7.22.0</td>
+    <td>7.22.0</td>
+  </tr>
 </table>
 
 \* For these versions, use the following Maven coordinates: