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/pypi.yaml

@@ -9,7 +9,7 @@ jobs:
   publish:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Set up Python
         uses: actions/setup-python@v4

.github/workflows/pythonpackage.yml

@@ -43,7 +43,7 @@ jobs:
                         version: "3.6"
                         conda: false
         steps:
-            -   uses: actions/checkout@v3
+            -   uses: actions/checkout@v4
 
             -   name: Setup Conda
                 if: matrix.conda == true
@@ -120,7 +120,7 @@ jobs:
     Linting:
         runs-on: ubuntu-latest
         steps:
-            -   uses: actions/checkout@v3
+            -   uses: actions/checkout@v4
 
             -   name: Set up Python on ubuntu-latest
                 uses: actions/setup-python@v4