[CI] remove duplicated env creation

Author: CSY-ModelCloud

.github/workflows/unit_tests.yml

@@ -289,7 +289,6 @@ jobs:
       - name: Clear installer cache on failure
         if: failure()
         run: |
-          echo "RETRY_INSTALL=true" >> $GITHUB_ENV
           source "${{ matrix.env_name }}/bin/activate"
 
           INSTALL_CMD='${{ matrix.install_cmd }}'
@@ -305,7 +304,6 @@ jobs:
       - name: retry ${{ matrix.name }}
         if: failure()
         run: |
-          uv venv "${{ matrix.env_name }}"
           source "${{ matrix.env_name }}/bin/activate"
           if [[ "${{ matrix.use_pip }}" == "true" ]]; then
             uv pip install pip -U