Bump actions/checkout from 2 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v3)

---
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/black.yml

@@ -11,7 +11,7 @@ jobs:
   formatting:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       # use black github action see https://black.readthedocs.io/en/stable/integrations/github_actions.html
       - uses: psf/black@stable

.github/workflows/regression.yml

@@ -16,7 +16,7 @@ jobs:
         python-version: [3.6, 3.7, 3.8]
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup Python ${{ matrix.python-version }}
       uses: actions/setup-python@v2
@@ -34,7 +34,7 @@ jobs:
         coverage run -m pytest -vra tests/
         coverage report -m
 
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Setup tmate session
       uses: mxschmitt/action-tmate@v3
       if: ${{ failure() }}

.github/workflows/urlchecker.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: URLs-checker
       uses: urlstechie/urlchecker-action@0.2.1
       with: