Update Python version in workflow to 3.14

Author: cclauss

.github/workflows/pip_install_on_python_prerelease.yml

@@ -14,7 +14,7 @@ jobs:
     - uses: actions/checkout@v5
     - uses: actions/setup-python@v6
       with:
-        python-version: 3.14.0-rc.3
+        python-version: 3.14
         allow-prereleases: true
     - run: pip install --upgrade pip
     - run: pip install ffpyplayer