build(deps): bump actions/setup-python from 5.1.0 to 5.6.0

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 5.1.0 to 5.6.0.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](actions/setup-python@v5.1.0...a26af69)

---
updated-dependencies:
- dependency-name: actions/setup-python
  dependency-version: 5.6.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/build-xapian.yml

@@ -46,7 +46,7 @@ jobs:
 
         # Setup version of Python to use
       - name: Set Up Python 3.13
-        uses: actions/setup-python@82c7e631bb3cdc910f68e0081d67478d79c6982d # v5.1.0
+        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
         with:
           python-version: 3.13
           allow-prereleases: true