Replace wait_for_requests with targeted waiter

Asherah Connorrequested to merge
kiv/replace-wait-for-requests-with-targeted-waiter into master

What does this MR do and why?

Replace an instance of wait_for_requests with a targeted waiter.

The board puts filter parameters into the URL after the query resolves, so it tells us when we're actually ready to proceed.

Also fix a NoMethodError that kept coming up (144 out of 300 flake events in the last 3 months) when there were no query parameters to decode.

Part of Remove all uses of `wait_for_requests`, `wait_f... (&22879) — I'll be monitoring the spec's flake rate over time to ensure this has the intended effect.

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