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/ci-testing.yml

@@ -29,7 +29,7 @@ jobs:
       HOROVOD_WITHOUT_MXNET: 1
       HOROVOD_WITHOUT_TENSORFLOW: 1
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v4
       with:

.github/workflows/cleanup-caches.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Cleanup
         run: |

.github/workflows/docs-deploy.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
     - name: Checkout 🛎️
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         persist-credentials: false
     - uses: actions/setup-python@v4

.github/workflows/release-pypi.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: actions/setup-python@v4
       with:
         python-version: 3.8