Sheets `clear` operation breaks with HTTP/2

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### A screenshot that you have tested with "Try this API".

N/A

### Link to the code that reproduces this issue. A link to a **public** Github Repository or gist with a minimal reproduction.

https://gist.github.com/neil-lobo/e632aae751fe7aec8bbc29a42c585015

### A step-by-step description of how to reproduce the issue, based on the linked reproduction.

1. Save `credentials.json` file with correct access to sheet to root of project
2. Replace `[sheet ID]` with accessible sheet
3. Run script
4. Observe output
5. Turn off http2
6. Observe output
### A clear and concise description of what the bug is, and what you expected to happen.

Using the http2 option, the clear operation does not work. I assume https://github.com/googleapis/google-api-nodejs-client/issues/1801#issuecomment-524921412 is no longer the case since there is an explicit option to enable http2 now.

Referring to the gist, the expected output is
```
finish get 200
finish clear 200

```

however the output is
```
finish get 200

```

Disabling http2 produces the correct output. Note that this is not simply a response issue, the operation itself does not reflect in the specified sheet.

### A clear and concise description WHY you expect this behavior, i.e., was it a recent change, there is documentation that points to this behavior, etc. **

Breaks usage

Commencez par le gist public lié et reproduisez l’opération clear de Sheets avec HTTP/2 activé, puis comparez-la au comportement fonctionnel de HTTP/1.1. Suivez le chemin client utilisé par le gist et vérifiez la correction en observant une réponse clear réussie et en constatant que la sheet spécifiée est effectivement vidée.

Rédigé par le modèle d'indexation à partir du texte de l'issue.