CI: Attempt to enable codecov again (danmar#7034)

Author: danmar

.github/workflows/coverage.yml

@@ -19,8 +19,6 @@ jobs:
   build:
 
     runs-on: ubuntu-22.04
-    # FIXME: disabled because the tokenless upload suddenly started to permanently fail
-    if: false # ${{ github.repository_owner == 'danmar' }}
 
     steps:
       - uses: actions/checkout@v4
@@ -62,9 +60,9 @@ jobs:
          name: Coverage results
          path: coverage_report
 
-      - uses: codecov/codecov-action@v3
+      - uses: codecov/codecov-action@v4
         with:
-          # token: ${{ secrets.CODECOV_TOKEN }} # not required for public repos
+          token: ${{ secrets.CODECOV_TOKEN }}
           # file: ./coverage.xml # optional
           flags: unittests # optional
           name: ${{ github.repository }} # optional