Integration tests: Suppress Chromium install log (and other Percy noise that isn't errors)

Created by: umpox

Description

We often get errors when trying to sending failing test logs to Buildkite.

Example failure: https://buildkite.com/sourcegraph/sourcegraph/builds/142872#ded1844b-649a-4b71-a944-fd42391f8f6c/2126-2130

This PR:

• Adds --quiet to our percy exec commands.
  • This will suppress any noisy logs (particularly the Chromium install logs)
  • Will only log errors, which I think is OK as that's what we primarily care about checking in our CI logs
  • Note: Does not suppress logs from our actual integration tests + Puppeteer (we definitely want those)

Follow up on https://github.com/sourcegraph/sourcegraph/pull/34262

Test plan

• Checked in CI. No Chromium logs, and we can easily now view the entire logs (Buildkite doesn't hide them)

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.