Bump actions/checkout from 2 to 3 (#341)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v3)

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

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Joran R. Angevaare <jorana@nikhef.nl>

.github/workflows/Pipi.yml

@@ -15,7 +15,7 @@ jobs:
         with:
           python-version: '3.8'
       - name: Checkout repo
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Install dependencies
         run: pip install wheel
       - name: Build package

.github/workflows/pytest.yml

@@ -49,7 +49,7 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
       - name: Checkout repo
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Install requirements for tests and latest strax
         run: |
             pip install git+https://github.com/NESTCollaboration/nestpy.git@v1.5.0