fix: revert incorrect build.yml changes - Base Setup doesn't provide jlpm

The previous commit attempted to add a 'Install dependencies' step using jlpm,
but jlpm is not available after Base Setup alone. The correct fix requires
updating yarn.lock locally with the cspell dependency, which is blocked by
missing GITHUB_TOKEN in the development environment.

This commit reverts the incorrect build.yml changes. The spell-check job
still needs yarn.lock to be updated with the cspell@9.2.1 dependency.

Author: devin-ai-integration[bot]

.github/workflows/build.yml

@@ -180,10 +180,5 @@ jobs:
       - name: Base Setup
         uses: jupyterlab/maintainer-tools/.github/actions/base-setup@v1
 
-      - name: Install dependencies
-        run: jlpm
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
       - name: Run spell check
         run: jlpm run spell-check