ci: update codecov GitHub action to 5.1.1

Author: nh13

.github/workflows/unittests.yaml

@@ -23,7 +23,7 @@ jobs:
           set -e
           sbt +clean coverage +test && sbt coverageReport coverageAggregate && (find $HOME/.sbt -name "*.lock" | xargs rm) && (find $HOME/.ivy2 -name "ivydata-*.properties" | xargs rm)
       - name: Code Coverage
-        uses: codecov/codecov-action@v3.1.0
+        uses: codecov/codecov-action@v5.1.1
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           flags: unittests # optional