Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/deploy-docs.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
     - name: checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
 

.github/workflows/pypi.yml

@@ -17,7 +17,7 @@ jobs:
   packages:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Set up Python
       uses: actions/setup-python@v4

.github/workflows/tests.yml

@@ -15,7 +15,7 @@ jobs:
       fail-fast: false
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Setup Micromamba ${{ matrix.python-version }}
       uses: mamba-org/setup-micromamba@v1