ci: restore coverage step in test workflow (#5752)

I think the step to upload coverage to coveralls has been getting 
skipped due to a mismatch in platform name.

.github/workflows/test.yaml

@@ -85,7 +85,7 @@ jobs:
         run: make cover
 
       - uses: jandelgado/gcov2lcov-action@4e1989767862652e6ca8d3e2e61aabe6d43be28b
-        if: matrix.platform == 'ubuntu-22.04'
+        if: matrix.platform == 'ubuntu-latest'
         name: convert coverage to lcov
         with:
           infile: coverage.txt
@@ -93,7 +93,7 @@ jobs:
 
       - name: upload to coveralls
         uses: coverallsapp/github-action@648a8eb78e6d50909eff900e4ec85cab4524a45b
-        if: matrix.platform == 'ubuntu-22.04'
+        if: matrix.platform == 'ubuntu-latest'
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           path-to-lcov: coverage.lcov