Update actions/cache action to v4 (#58)

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This PR contains the following updates:

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

---

### Release Notes

<details>
<summary>actions/cache (actions/cache)</summary>

### [`v4`](https://togithub.com/actions/cache/compare/v3...v4)

[Compare Source](https://togithub.com/actions/cache/compare/v3...v4)

</details>

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.github/workflows/ci.yaml

@@ -55,7 +55,7 @@ jobs:
       # faster to download again than to fetch them from the GitHub actions
       # cache.
       - name: Mount bazel caches
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: |
             ~/.cache/bazel