fix(ci): use ubuntu-latest container for gitleaks scan

Switch Gitleaks job to docker container execution to satisfy actions/checkout Node.js dependency.

.gitea/workflows/test-ci.yml

@@ -15,13 +15,12 @@ jobs:
 
   gitleaks-scan:
     name: Secret Detection (Gitleaks)
-    runs-on: host
+    runs-on: ubuntu-latest
     steps:
-      - name: Fetch Code
-        run: |
-          git config --global --add safe.directory "$PWD"
-          git fetch --all
-          git checkout $GITEA_SHA
+      - name: Check Out Code
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
 
       - name: Run Gitleaks Scan
         run: |