fix(system-upgrades): Fix broken execution of scripts

infrastructure/system-upgrades/kubernetes.yaml

@@ -26,8 +26,8 @@ stringData:
     set -e
     set -x
     secrets="$(dirname "$0")"
-    $secrets/setup-copr.sh
-    $secrets/kubernetes-upgrade.sh
+    source "$secrets/setup-copr.sh"
+    source "$secrets/kubernetes-upgrade.sh"
 ---
 apiVersion: upgrade.cattle.io/v1
 kind: Plan