chore(ci): use pipx for detect-secrets install

Author: vredchenko

.github/workflows/leaked-secrets-scan.yml

@@ -19,15 +19,8 @@ jobs:
       uses: actions/checkout@v6
       with:
         fetch-depth: 0
-    - name: Set up Python
-      uses: actions/setup-python@v6
-      with:
-        python-version: '3.12'
-        cache: 'pip'
     - name: Install detect-secrets
-      run: |
-        python -m pip install --upgrade pip
-        pip install detect-secrets
+      run: pipx install detect-secrets
     - name: Verify baseline exists
       run: |
         if [ ! -f .secrets.baseline ]; then