Bump actions/checkout from 2 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...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>

.github/workflows/build_docs.yml

@@ -10,7 +10,7 @@ jobs:
   build-docs:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
 
     - name: Set up Python
       uses: actions/setup-python@v2

.github/workflows/codespell.yml

@@ -17,6 +17,6 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Codespell
         uses: codespell-project/actions-codespell@v2

.github/workflows/deploy_pypi.yml

@@ -14,7 +14,7 @@ jobs:
   deploy-pypi:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: actions/setup-python@v2
 
     - name: Get versions

.github/workflows/run_tests.yml

@@ -15,7 +15,7 @@ jobs:
       max-parallel: 5
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Python
       uses: actions/setup-python@v2
       with: