Bump actions/setup-python from 5 to 6

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 5 to 6.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](actions/setup-python@v5...v6)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -132,7 +132,7 @@ jobs:
         steps:
         -   uses: actions/checkout@v5
         -
-            uses: actions/setup-python@v5
+            uses: actions/setup-python@v6
             with:
                 python-version: '3.x'
         -   name: "Main Script"
@@ -202,7 +202,7 @@ jobs:
             runs-on: ubuntu-latest
             steps:
             -   uses: actions/checkout@v5
-            -   uses: actions/setup-python@v5
+            -   uses: actions/setup-python@v6
             -   run: |
                     pip install cffconvert
                     cffconvert -i CITATION.cff --validate