fix(github-actions.mdx): remove extraneous build step from parallel example (#5304)

Fix example basic parallelization example by removing the `build` command from the `cypress-run` job, because including the `build` step overrwrites the existing use of `actions/download-artifact` and thereby undermines the build cacheing used in the `install` job

Co-authored-by: Paul Jaffre <[email protected]>

Author: itsalaidbacklife

docs/guides/continuous-integration/github-actions.mdx

@@ -376,7 +376,6 @@ jobs:
       - name: Cypress run
         uses: cypress-io/github-action@v5
         with:
-          build: npm run build
           record: true
           parallel: true
           start: npm start