fix sed command for outgoing mail

.gitlab-ci.yml

@@ -359,7 +359,7 @@ install-stackspin:
     - sed -i "s/example.org/$FQDN/"  ${CLUSTER_DIR}/.flux.env
     - sed -i "/^\s*#.*$/d; /^\s*$/d" ${CLUSTER_DIR}/.flux.env
     # Disable outgoing mail
-    - sed -i "s/outgoing_mail_enabled=true/outgoing_mail_enabled=false" ${CLUSTER_DIR}/.flux.env
+    - sed -i "s/outgoing_mail_enabled=true/outgoing_mail_enabled=false/" ${CLUSTER_DIR}/.flux.env
     # Deploy secret/stackspin-cluster-variables
     - cp install/kustomization.yaml ${CLUSTER_DIR}
     - kubectl create namespace flux-system