docs: fix default value

README.md

@@ -46,7 +46,7 @@ The Python template uses some global configuration used throughout all jobs.
 | -------------------- | ------------------------------------------------------------------------------------- | ------------------ |
 | `image` / `PYTHON_IMAGE` | The Docker image used to run Python <br/>:warning: **set the version required by your project** | `registry.hub.docker.com/library/python:3` |
 | `project-dir` / `PYTHON_PROJECT_DIR` | Python project root directory                                                         | `.`                |
-| `build-system` / `PYTHON_BUILD_SYSTEM`| Python build-system to use to install dependencies, build and package the project (see below) | _none_ (auto-detect) |
+| `build-system` / `PYTHON_BUILD_SYSTEM`| Python build-system to use to install dependencies, build and package the project (see below) | `auto` (auto-detect) |
 | `PIP_INDEX_URL`      | Python repository url                                                                 | _none_             |
 | `PIP_EXTRA_INDEX_URL` | Extra Python repository url                                                           | _none_             |
 | `pip-opts` / `PIP_OPTS` | pip [extra options](https://pip.pypa.io/en/stable/cli/pip/#general-options)     | _none_             |