Remove superfluous namespace flag for cert-manager override

.gitlab-ci.yml

@@ -378,7 +378,7 @@ install-stackspin:
     - kubectl apply -k ${CLUSTER_DIR}
     # Add an override so cert-manager uses the SSL.com ClusterIssuer
     - kubectl create namespace cert-manager
-    - kubectl apply -n cert-manager -f ./install/overrides/stackspin-cert-manager-override.yaml
+    - kubectl apply -f ./install/overrides/stackspin-cert-manager-override.yaml
     # Install flux and general, non-app specific secrets
     - bash ./install/install-stackspin.sh
   extends: