docs(bigquery): remove location parameter from samples

[plamut]

Closes#9499.

The parameter can sometimes confuse new BigQuery developers. Since location autodetection now works pretty well, the parameter can be removed from code samples for better clarity.

There didn't seem to be any samples specifically demonstrating how to set the location, thus removed that parameter from all of them.

PR checklist

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

[emar-kar]

As I'm working with the refactoring project of the BigQuery samples, your PR might cause conflicts with the already existing one. There is a link to it in the issue.

[plamut]

@emar-kar Thanks for the notice. I see that the samples have been split into multiple modules. I can make the same set of changes based on the existing PR, and submit my PR to the other PR branch. Then we can merge both set of changes into the main repository without conflicts.

[emar-kar]

It will be great! And you can leave the snippets.py without changes because it is under deprecation and as soon as I'm making a new sample file, I'm deleting the same test from it.

[plamut]

Superseded by a pull request opened directly against a related pull request to avoid unnecessary merge conflicts in the samples code.