ci: shell declaration in composite actions

Author: hleb-rubanau

.github/actions/setup-python-pip-tox/action.yml

@@ -11,6 +11,8 @@ runs:
     - uses: actions/setup-python@v6
       with:
         python-version: ${{ inputs.python }}
-    - run: |
+    - name: upgrade pip and install tox
+      shell: bash
+      run: |
         python -m pip -q install --upgrade pip "setuptools==65.6.2"
         pip -q install "tox<4" tox-gh-actions

.github/actions/setup-rust-poetry/action.yml

@@ -15,6 +15,7 @@ runs:
       restore-keys: |
         ${{ runner.os }}-poetry-
     - name: install Rust and Poetry 
+      shell: bash
       run : |
         curl https://sh.rustup.rs -sSf | sh -s -- -y --default-toolchain stable --profile minimal
         source "$HOME/.cargo/env"