Pass multiple variables in trigger pipeline example

What does this MR do?

I needed this recently and even with all my experience it took me quite some time, many attempts and a lot of googling to figure out the proper way to do this. I found this prior discussion on the topic with some pretty knowledgable experts also struggling to define the correct way back then, and the solutions suggested in there didn't work for me anymore.

Passing multiple variables in this call at once is pretty much the only somewhat complex/hard to figure out part of this, so I really think our example should show one confirmed working way of how to do it.

Also a very minor thing: The project ID in the example response now matches the project of the example call.

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