ci: fix Pulumi CLI install action

Replace non-existent pulumi/actions-install@v1 with
pulumi/setup-pulumi@v2, the official action for installing the
Pulumi CLI without running a command.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: hugbubby

.github/workflows/deploy.yml

@@ -401,7 +401,7 @@ jobs:
         run: pnpm install --frozen-lockfile
 
       - name: Install Pulumi CLI
-        uses: pulumi/actions-install@v1
+        uses: pulumi/setup-pulumi@v2
 
       - name: Configure kubeconfig
         shell: bash