Bump actions/checkout from 3 to 4 (#470)

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

Author: dependabot[bot]

.github/workflows/ci.yaml

@@ -29,7 +29,7 @@ jobs:
         os: ["ubuntu-latest"]
         python-version: ["3.8", "3.11"]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0 # Fetch all history for all branches and tags.
       - name: Set environment variables
@@ -69,7 +69,7 @@ jobs:
       matrix:
         python-version: ["3.10"]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0 # Fetch all history for all branches and tags.
       - name: Set environment variables
@@ -106,7 +106,7 @@ jobs:
       run:
         shell: bash -l {0}
     steps:
-      - 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
@@ -134,7 +134,7 @@ jobs:
       matrix:
         python-version: ["3.8", "3.11"]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0 # Fetch all history for all branches and tags.
       - name: Set up conda environment

.github/workflows/pypi.yaml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.repository == 'xarray-contrib/cf-xarray'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - uses: actions/setup-python@v4

.github/workflows/testpypi-release.yaml

@@ -17,7 +17,7 @@ jobs:
     if: ${{ contains( github.event.pull_request.labels.*.name, 'test-build') && github.event_name == 'pull_request' || github.event_name == 'workflow_dispatch' }}
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
 

.github/workflows/upstream-dev-ci.yaml

@@ -31,7 +31,7 @@ jobs:
       matrix:
         python-version: ["3.11"]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0 # Fetch all history for all branches and tags.
       - name: Set environment variables