ci: bump actions/setup-python from 2 to 6 (#320)

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 2 to 6.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](actions/setup-python@v2...v6)

---
updated-dependencies:
- dependency-name: actions/setup-python
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
           submodules: recursive
           fetch-depth: 0
           fetch-tags: true
-      - uses: actions/setup-python@v3
+      - uses: actions/setup-python@v6
         with:
           python-version: 3.12
       - uses: pre-commit/action@v3.0.0

.github/workflows/docs.yml

@@ -17,7 +17,7 @@ jobs:
         with:
           submodules: recursive
 
-      - uses: actions/setup-python@v2
+      - uses: actions/setup-python@v6
         with:
           python-version: 3.12