Clarify the use of the sample foxes corpus in Sidekicks DocQA

[benlower]

In https://docs.ai-jsx.com/sidekicks/sidekicks-docsqa change Example Corpus note to be:

Rather than creating a corpus from scratch, you can also query an existing corpus that has a bunch of web pages with exciting facts about foxes. This corpus has ID 44094d5a-f817-4c2e-a2a4-8f8a0c936d0f and can be used in your code if you don't want to take the time to create a corpus of your own. If that is the case, you can jump ahead to the section below titled "Querying the Corpus" (https://docs.ai-jsx.com/sidekicks/sidekicks-docsqa#querying-the-corpus). Otherwise, you can continue with "Adding Sources to the Corpus" and make your own corpus to use.

[adriatic]

I am now continuing following the tutorial document section as if this change is already deployed