Revert "Bump actions to node 20 (#3461)" (#3462)

This reverts commit defeb8e52b.

As per https://github.com/actions/upload-artifact/issues/478 the new version of upload-artifact includes a breaking change.

.github/workflows/sec_sast_flawfinder.yml

@@ -16,7 +16,7 @@ jobs:
     steps:
       # step 1
       - name: clone application source code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v3
 
       # step 2
       - name: flawfinder_scan
@@ -27,7 +27,7 @@ jobs:
 
       # step 3
       - name: save report as pipeline artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3
         with:
           name: flawfinder_report.sarif
           path: flawfinder_report.sarif