[patch] add db2_channel to update pipeline

Author: terc1997

src/mas/devops/templates/pipelinerun-update.yml.j2

@@ -46,6 +46,8 @@ spec:
       value: "{{ db2_namespace }}"
     - name: db2_v12_upgrade
       value: "{{ db2_v12_upgrade }}"
+    - name: db2_channel
+      value: "{{ db2_channel }}"
 {%- endif %}
 {%- if mongodb_namespace is defined and mongodb_namespace != "" %}