BigQuery: Dependency pins may be inadequate

When this PR, https://github.com/googleapis/google-cloud-python/pull/9915, shipped as `google-cloud-core=1.1.0` the core dep likely needs the minimum version rev'd

```
    "google-auth >= 1.9.0, < 2.0dev",
    "google-api-core >= 1.15.0, < 2.0dev",
    "google-cloud-core >= 1.0.3, < 2.0dev"
```