BigQuery Snippets: Use autodetected location

[grant]

Use autodetected location.

In the example provided, it is written that The location must be specified, but the example works even without setting location for datasets located in US and asia-northeast1. Whether specifying location for an upload job is an absolute requirement or not is affecting an application I'm working on. Can you provide details?

See b/116968956

[tswast]

Can you add a snippet such as googleapis/google-cloud-python#8422 that does show how to override this?

[grant]

@tswast I can't add a new snippet. That's not in scope of the sample I'm trying to standardize, fixing the attached bug.
I'm updating this snippet in a few languages.

I can change this PR to help fix the bug in some other way, but would like explicit instructions on how to do that.

[tswast]

Per the bug, if you aren't adding a new snippet (location autodetection is a new feature, after all), please add an explanation comment as we did in Java. googleapis/google-cloud-java#5475

[grant]

Like the Java snippet, I added a note that the location is inferred here.