ci: bump codecov to v4

Author: gnikit

.github/workflows/main.yml

@@ -56,7 +56,7 @@ jobs:
         shell: bash
 
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v4
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           fail_ci_if_error: true