fix: Update CI workflow to use ATCODER_REVEL_SESSION for environment setup

Author: yiwiy9

.github/workflows/ci.yml

@@ -20,8 +20,7 @@ jobs:
       - name: Setup .env file
         run: |
           cp .devcontainer/.env.example .devcontainer/.env
-          sed -i "s/your_atcoder_username_here/${{ secrets.ATCODER_USERNAME }}/g" .devcontainer/.env
-          sed -i "s/your_atcoder_password_here/${{ secrets.ATCODER_PASSWORD }}/g" .devcontainer/.env
+          sed -i "s/your_atcoder_session_here/${{ secrets.ATCODER_REVEL_SESSION }}/g" .devcontainer/.env
 
       - name: Login to GitHub Container Registry
         uses: docker/login-action@v3