CI: update checkout, setup-python and upload-artifact to v7

actions/checkout v6 hands the Windows path of its credentials config to
git config --unset as a regex, which MSYS2's git rejects in the
ProxSpace job (actions/checkout#2528, fixed in v7.0.1). The
persist-credentials: false added for it did not help and is dropped.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/codeql-analysis.yml

@@ -53,7 +53,7 @@ jobs:
         if [ -f requirements.txt ]; then python3 -m pip install -r requirements.txt; fi
 
     - name: Checkout repository
-      uses: actions/checkout@v6
+      uses: actions/checkout@v7
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL