Remove Shell scripts under airflow/www from releases (#16588)

We don't need the following files:

- `airflow/www/compile_assets.sh`
- `airflow/www/ask_for_recompile_assets_if_needed.sh`

So we exclude them from sdist and wheel

(cherry picked from commit 7af18ac)

MANIFEST.in

@@ -30,6 +30,7 @@ graft airflow/config_templates
 recursive-exclude airflow/www/node_modules *
 global-exclude __pycache__  *.pyc
 exclude airflow/www/yarn.lock
+exclude airflow/www/*.sh
 include airflow/alembic.ini
 include airflow/api_connexion/openapi/v1.yaml
 include airflow/git_version