Bump actions/checkout from 3 to 4 (#226)

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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci-additional.yml

@@ -19,7 +19,7 @@ jobs:
     if: github.repository == 'xarray-contrib/pint-xarray'
     steps:
     - name: checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
     - name: setup python
       uses: actions/setup-python@v4
       with:

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
     outputs:
       triggered: ${{ steps.detect-trigger.outputs.trigger-found }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         fetch-depth: 2
     - uses: xarray-contrib/ci-trigger@v1
@@ -49,7 +49,7 @@ jobs:
 
     steps:
     - name: checkout the repository
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         # need to fetch all tags to get a correct version
         fetch-depth: 0  # fetch all branches and tags

.github/workflows/nightly.yml

@@ -22,7 +22,7 @@ jobs:
     outputs:
       triggered: ${{ steps.detect-trigger.outputs.trigger-found }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         fetch-depth: 2
     - uses: xarray-contrib/[email protected]
@@ -54,7 +54,7 @@ jobs:
 
     steps:
     - name: checkout the repository
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         # need to fetch all tags to get a correct version
         fetch-depth: 0  # fetch all branches and tags

.github/workflows/pypi.yaml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.repository == 'xarray-contrib/pint-xarray'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python
         uses: actions/setup-python@v4
         with: