Install Python 3.13, except for nightly-latest

Author: mbg

.github/workflows/__multi-language-autodetect.yml

@@ -5,6 +5,12 @@ env:
   CODEQL_ACTION_RESOLVE_SUPPORTED_LANGUAGES_USING_CLI: true
 installGo: true
 steps:
+  - name: Install Python 3.13
+    if: matrix.version != 'nightly-latest'
+    uses: actions/setup-python@v6
+    with:
+      python-version: '3.13'
+
   - name: Use Xcode 16
     if: runner.os == 'macOS' && matrix.version != 'nightly-latest'
     run: sudo xcode-select -s "/Applications/Xcode_16.app"