Update GitHub Actions workflow to set working directory for migrations

- Added a working-directory specification for the 'Run migrations' step in the GitHub Actions workflow, ensuring that Diesel migrations are executed in the correct context within the './api' directory. This change enhances the reliability of the migration process during deployment.

.github/workflows/porter_app_staging_3155.yml

@@ -40,6 +40,7 @@ jobs:
           aws s3 cp ${{ secrets.CERT_S3_URL }} ~/.postgresql/root.crt
 
       - name: Run migrations
+        working-directory: ./api
         run: diesel migration run
         env:
           DATABASE_URL: ${{ secrets.DB_URL }}