fix(netpol): use default namespace

[revolunet]

Use namespace from environment if not provided

Allow usage of:

import { create } from "@socialgouv/kosko-charts/components/netpol";

export default create();

[github-actions[bot]]

:tada: This PR is included in version 9.8.10 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: