fix(actions): install kubectl before creating test cluster

.forgejo/workflows/validate.yaml

@@ -41,7 +41,10 @@ jobs:
           curl -fsSL -o /tmp/k3d https://github.com/k3d-io/k3d/releases/download/v5.7.4/k3d-linux-amd64
           chmod +x /tmp/k3d
           mv /tmp/k3d /usr/local/bin
-
+      - name: Install kubectl
+        run: |
+          curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
+          chmod +x kubectl mv kubectl /usr/local/bin
       - name: Create test cluster
         run: |
           k3d cluster create test --wait