prepare.yml in mnconvert-1.64.0

- old
+ new

@@ -20,10 +20,11 @@
       - run: mkdir ieee
 
       - uses: actions/checkout@v3
         with:
           repository: metanorma/ieee-stl
+          ref: main
           token: ${{ secrets.pat_token || github.token }}
           path: ieee/stl
 
       - uses: actions/checkout@v3
         with:
@@ -40,10 +41,10 @@
         with:
           source-path: ieee/samples
           use-bundler: true
           agree-to-terms: true
 
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         with:
           name: ieee-test-input
           path: |
             ieee/stl/standards-1-7-DTD/standards-1-7-dtd/
             ieee/samples/_site/documents/p987.6/document.xml