Update actions/checkout action to v4 (#114)

[![Mend
Renovate](https://app.renovatebot.com/images/banner.svg)](https://renovatebot.com)

This PR contains the following updates:

| Package | Type | Update | Change |
| --------------------------------------------------------- | ------ |
------ | ------------ |
| [actions/checkout](https://togithub.com/actions/checkout) | action |
major | `v3` -> `v4` |

---

### Release Notes

<details>
<summary>actions/checkout (actions/checkout)</summary>

###
[`v4`](https://togithub.com/actions/checkout/blob/HEAD/CHANGELOG.md#v400)

[Compare Source](https://togithub.com/actions/checkout/compare/v3...v4)

- [Support fetching without the --progress
option](https://togithub.com/actions/checkout/pull/1067)
- [Update to node20](https://togithub.com/actions/checkout/pull/1436)

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [x] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR has been generated by [Mend
Renovate](https://www.mend.io/free-developer-tools/renovate/). View
repository job log [here](https://developer.mend.io/github/ilkka/nisse).


<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNi45Ny4xIiwidXBkYXRlZEluVmVyIjoiMzYuOTcuMSIsInRhcmdldEJyYW5jaCI6InRydW5rIn0=-->

.github/workflows/build_and_push.yml

@@ -13,7 +13,7 @@ jobs:
  name: Build and publish image
  runs-on: ubuntu-latest
  steps:
- - uses: actions/checkout@v3
+ - uses: actions/checkout@v4
  - name: Build and push
  uses: docker/build-push-action@v5.0.0
  with:

.github/workflows/docs.yml

@@ -10,7 +10,7 @@ jobs:
  UML_FILES: "**.wsd"
  OUTPUT_DIR: "docs"
  steps:
- - uses: actions/checkout@v3
+ - uses: actions/checkout@v4
  with:
  fetch-depth: 1
  - name: Make sure output directory exists

.github/workflows/test-pr.yml

@@ -10,7 +10,7 @@ jobs:
  runs-on: ubuntu-latest
 
  steps:
- - uses: actions/checkout@v3
+ - uses: actions/checkout@v4
  - name: Set up Elixir
  uses: erlef/setup-beam@v1
  with: