[Fix] Cypress metadata test fails intermittently after saved question updates

[openroomote-bruno]

​Created by Roomote. View the task or mention @roomote for follow-up asks.

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Description

The metabase#43216 Cypress scenario no longer assumes dependent-card metadata will propagate within 450 ms. It captures the target question ID and polls its query-metadata endpoint until the expected D field is present, with a shared 10-second deadline and short request timeouts.

This removes an explicitly marked flaky timing assumption and synchronizes the test on the backend state that its later UI assertions require. This is test-only maintenance with no product behavior change.

How to verify

1. Run e2e/test/scenarios/question-reproductions/reproductions-2.cy.spec.js in a provisioned Metabase Cypress environment.
2. Confirm the source question update propagates to the target question before the target UI assertions run.

The sandbox has no node_modules/.bin/cypress or application stack, so the Cypress scenario could not be executed here. node --check e2e/test/scenarios/question-reproductions/reproductions-2.cy.spec.js and git diff --check passed.

Demo

Not applicable: this changes E2E synchronization only.

Checklist

• Tests have been updated to cover changes in this PR
• If adding new Loki tests: they pass stress testing