deps: update codecov/codecov-action action to v4 (#359)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [codecov/codecov-action](https://togithub.com/codecov/codecov-action)
| action | major | `v3` -> `v4` |

---

### Release Notes

<details>
<summary>codecov/codecov-action (codecov/codecov-action)</summary>

### [`v4`](https://togithub.com/codecov/codecov-action/compare/v3...v4)

[Compare
Source](https://togithub.com/codecov/codecov-action/compare/v3...v4)

</details>

---

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are satisfied.

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rebase/retry checkbox.

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---

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.github/workflows/test.yml

@@ -29,4 +29,6 @@ jobs:
         run: tox -- --cov --cov-report=xml
 
       - name: Upload coverage reports to Codecov
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v4
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}