Update the pytest timeout from 10min to 15min for python tests

[mikealfare]

Problem

One of the python model tests takes just over 10 minutes to complete when run locally. However, we specify a timeout of 10 minutes in tox.ini.

Solution

Bump the timeout from 10 minutes to 15 minutes to allow the test to complete. This doesn't appear to be an issue in newer versions of dbt-bigquery, so it's not necessary to apply this change to newer versions.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-bigquery contributing guide.