Don't use deprecated flag for upgrade

Signed-off-by: Dimitris Karakasilis <dimitris@karakasilis.me>

tests/upgrade_cli_test.go

@@ -60,7 +60,7 @@ var _ = Describe("k3s upgrade manual test", Label("upgrade-with-cli"), func() {
 			Expect(currentVersion).To(ContainSubstring("v"))
 
 			By(fmt.Sprintf("Upgrading to: %s", containerImage))
-			out, err := vm.Sudo("kairos-agent --debug upgrade --force --image " + containerImage)
+			out, err := vm.Sudo("kairos-agent --debug upgrade --force --source " + containerImage)
 			Expect(err).ToNot(HaveOccurred(), string(out))
 			Expect(out).To(ContainSubstring("Upgrade completed"))
 			Expect(out).To(ContainSubstring(containerImage))