Update codecov action

Author: S7evinK

.github/workflows/tests.yml

@@ -50,7 +50,10 @@ jobs:
             ${{ runner.os }}-go${{ matrix.go }}-test-
       - run: go test -race -coverpkg=./... -coverprofile=cover.out $(go list ./...)
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v4
+        with:
+          fail_ci_if_error: true
+          token: ${{ secrets.CODECOV_TOKEN }}
 
   # run go test on Dendrite with different go versions
   test-dendrite: