Add `JWTInput` as a valid type of the options for `BigQuery` constructor

[IvanaGyro]

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1. Is this a client library issue or a product issue? client library

2. Did someone already solve this? No

3. Do you have a support contract? No

If the support paths suggested above still do not result in a resolution, please provide the following details.

Environment details

• OS: Windows WSL (Ubuntu 22.04)
• Node.js version: 18.15.0
• npm version: yarn v1.22.19
• @google-cloud/bigquery version: 6.2.0

Steps to reproduce

In the example of user auth, an object passed to BigQuery's constructor is not defined in the type definition of this repository. I found there is a similar type JWTInput defined in google-auth-library-nodejs. Can JWTInput be added as a member of BigQueryOptions to make the logic implementation consistent with the type definition?