CI: Bump to codecov-action@v4

Author: okurz

.github/workflows/ci-tests.yaml

@@ -37,7 +37,7 @@ jobs:
         run: |
           TEST_SHARED=1 TEST_SUBREAPER=1 cover -test -report codecovbash
       - name: Upload coverage to ☂️ Codecov
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v4
         if: matrix.perl == 'latest'
         with:
           file: cover_db/codecov.json