fix broken URL in unit.yaml GH action (#2335)

Signed-off-by: Josef Karasek <jkarasek@redhat.com>

.github/workflows/unit.yml

@@ -19,7 +19,7 @@ jobs:
         run: |
           os=$(go env GOOS)
           arch=$(go env GOARCH)
-          curl -L https://go.kubebuilder.io/dl/2.3.1/${os}/${arch} | tar -xz -C /tmp/
+          curl -L https://github.com/kubernetes-sigs/kubebuilder/releases/download/v2.3.1/kubebuilder_2.3.1_${os}_${arch}.tar.gz | tar -xz -C /tmp/
           sudo mv /tmp/kubebuilder_2.3.1_${os}_${arch} /usr/local/kubebuilder
       - name: Run unit tests
         run: make unit