github action: update to upload-artifact@v4

Author: lesismal

.github/workflows/autobahn.yml

@@ -32,7 +32,7 @@ jobs:
       - name: Autobahn Report Artifact
         if: >-
           startsWith(matrix.os, 'ubuntu')
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
 
         with:
           name: autobahn report ${{ matrix.go }} ${{ matrix.os }}