GHA: set allow-prereleases to true

Author: kislyuk

.github/workflows/ci.yml

@@ -15,6 +15,7 @@ jobs:
     - uses: actions/setup-python@v5
       with:
         python-version: ${{matrix.python-version}}
+        allow-prereleases: true
     - run: |
         if [[ $(uname) == Linux ]]; then sudo apt-get install --no-install-recommends python3-lxml python3-certifi; fi
     - run: make install