Missing 2.3.12 tag

The package published to [pypi](https://pypi.org/project/nbdev/) is versioned `2.3.12`, while the latest tag in this repo is `2.3.11`.
This makes `pre-commit` and the nbdev-ci workflow use different versions.

# Provide a minimally reproducible example

Using the `pre-commit` tool with `pre-commit-config.yaml`:

```yaml
repos:
- repo: https://github.com/fastai/nbdev
rev: 2.3.11
hooks:
- id: nbdev_clean
```

and `.github/workflows/test.yaml`:

```yaml
name: CI
on: [workflow_dispatch, pull_request]

jobs:
lint:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v3
- uses: actions/setup-python@v3
- uses: pre-commit/action@v3.0.0

test:
runs-on: ubuntu-latest
steps:
- uses: fastai/workflows/nbdev-ci@master
```

The `lint` job succeeds and the `test` job fails on the initial `00_core.ipynb`.

This is because that the `nbdev_clean` command cleans the initial notebook in `2.3.12` (which is used by the CI as it is published to [pypi](https://pypi.org/project/nbdev/)) while in `2.3.11` (which is the latest tag in [this repo](https://github.com/fastai/nbdev/tags)) it doesn't clean.

The nbdev-ci git action [installs the latest from pypi](https://github.com/fastai/workflows/blob/58444f475ebf4eee6c674808e9053c496a1c9ca8/nbdev-ci/action.yml#L45), while `pre-commit` installs from github, and so the versions differ.

This is confirmed by installing the specific versions and running `nbdev_clean`:

```bash
pip install nbdev=2.3.12
nbdev_clean
git status
# files will change
```
```bash
pip install nbdev=2.3.11
nbdev_clean
git status
# No files will change
```

# Proposed fixes

1. I can work around it by specifying the specific hash of version `2.3.12` (which should probably be 744a52d).

2. An easy fix would be to tag this commit as `2.3.12`.

3. A more permanent solution will be to enable version pining in the [ci workflow](https://github.com/fastai/workflows/), I might create a pull request for that in the coming days.

Vergleiche die Repository-Tags mit dem PyPI-Release 2.3.12 und untersuche den Commit 744a52d; überprüfe anschließend die Paketinstallation des nbdev-ci-Workflows und die pre-commit-Konfiguration. Als erledigt gilt die Aufgabe, wenn der Repository-Tag und die CI/pre-commit-Versionen übereinstimmen und die im gezeigten 00_core.ipynb enthaltenen Prüfungen erfolgreich sind.

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