fix: upload codecov report as a separate workflow step (openedx#1476)

.github/workflows/validate.yml

@@ -18,8 +18,26 @@ jobs:
       with:
         node-version: ${{ matrix.node }}
     - run: make validate.ci
+    - name: Archive code coverage results
+      uses: actions/upload-artifact@v4
+      with:
+        name: code-coverage-report-${{ matrix.node }}
+        # When we're only using Node 20, replace the line above with the following:
+        # name: code-coverage-report
+        path: coverage/*.*
+  coverage:
+    runs-on: ubuntu-latest
+    needs: tests
+    steps:
+    - uses: actions/checkout@v3
+    - name: Download code coverage results
+      uses: actions/download-artifact@v4
+      with:
+        name: code-coverage-report-20
+        # When we're only using Node 20, replace the line above with the following:
+        # name: code-coverage-report
     - name: Upload coverage
       uses: codecov/codecov-action@v4
       with:
         fail_ci_if_error: true
-        token: ${{ secrets.CODECOV_TOKEN }}
+        token: ${{ secrets.CODECOV_TOKEN }}