chore: Upgrade artifact management actions in Terraform workflow

- Updated the GitHub Actions workflow to use version 4 of the upload and download artifact actions, enhancing compatibility and performance.
- Ensured that the artifact management process remains consistent during the Terraform plan and apply stages.

Author: kanare-dev

.github/workflows/terraform.yml

@@ -180,7 +180,7 @@ jobs:
       # plan ジョブで作成した tfplan を apply ジョブに引き渡すためアーティファクトとして保存
       # main push 時のみアップロード（PR では apply は実行しない）
       - name: Upload plan artifact
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         if: steps.plan.outcome == 'success' && github.ref == 'refs/heads/main' && github.event_name == 'push'
         with:
           name: tfplan-${{ matrix.environment }}
@@ -254,7 +254,7 @@ jobs:
 
       # plan ジョブで保存した tfplan をダウンロード（PR で表示した内容と同一の変更を適用）
       - name: Download plan artifact
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: tfplan-dev
           path: terraform/environments/dev
@@ -300,7 +300,7 @@ jobs:
 
       # plan ジョブで保存した tfplan をダウンロード（PR で表示した内容と同一の変更を適用）
       - name: Download plan artifact
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: tfplan-prod
           path: terraform/environments/prod