http2: it should send data in a POST failed

[flaky-bot]

This test failed!

To configure my behavior, see the Flaky Bot documentation.

If I'm commenting on this issue too often, add the flakybot: quiet label and
I will stop commenting.

---

commit: b7491523d144cf916b62c53b7b994c886818104e
buildURL: Build Status, Sponge
status: failed

Test output

invalid_grant: Invalid JWT Signature.
Error: invalid_grant: Invalid JWT Signature.
    at Gaxios._request (node_modules/gaxios/build/src/gaxios.js:130:23)
        -> /workspace/node_modules/gaxios/src/gaxios.ts:158:15
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
    at async GoogleToken.requestToken (node_modules/gtoken/build/src/index.js:238:23)
    at async GoogleToken.getTokenAsync (node_modules/gtoken/build/src/index.js:145:20)
    at async JWT.refreshTokenNoCache (node_modules/google-auth-library/build/src/auth/jwtclient.js:172:23)
    at async JWT.getRequestMetadataAsync (node_modules/google-auth-library/build/src/auth/oauth2client.js:284:17)
    at async JWT.getRequestHeaders (node_modules/google-auth-library/build/src/auth/oauth2client.js:247:26)
    at async createAPIRequestAsync (build/src/apirequest.js:267:33)
        -> /workspace/src/apirequest.ts:321:27
    at async Context. (build/system-test/test.http2.js:54:24)
        -> /workspace/system-test/test.http2.ts:61:20