fix(deps): Update dependency @types/google-protobuf to v3.15.9 (#27)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [@types/google-protobuf](https://togithub.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/google-protobuf) ([source](https://togithub.com/DefinitelyTyped/DefinitelyTyped)) | devDependencies | patch | [`3.15.7` -> `3.15.9`](https://renovatebot.com/diffs/npm/@types%2fgoogle-protobuf/3.15.7/3.15.9) |

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