build: move steps to template dir

.github/workflows/templates/checks/action.yaml

@@ -7,17 +7,14 @@ runs:
       with:
         python-version: '3.10'
         cache: 'pip'
-      shell: bash
     - uses: extractions/setup-just@v1
       name: Setup just
-      shell: bash
     - name: Initialize Pants
       uses: pantsbuild/actions/init-pants@main
       with:
         # cache0 makes it easy to bust the cache if needed
         gha-cache-key: cache0-py310
         named-caches-hash: ${{ hashFiles('lockfiles/*.json', '**/something-else.lock') }}
-      shell: bash
     - name: format
       run: just fmt
       shell: bash