Do not require upstream ws in ici

Author: Felix Exner

.github/workflows/reusable_ici.yml

@@ -12,7 +12,7 @@ on:
 
       upstream_workspace:
         description: 'UPSTREAM_WORKSPACE variable for industrial_ci. Usually path to local .repos file.'
-        required: true
+        required: false
         type: string
       ros_distro:
         description: 'ROS_DISTRO variable for industrial_ci'