ci: Fix docker compose timeout behavior

[def-]

--timeout=0 used to mean "kill immediately", but since we upgraded Docker Compose it seems to have changed meaning to "wait forever"

Seen in https://buildkite.com/materialize/test/builds/113972#019b6fa9-0fda-41ce-8c36-5be94fa1c0f5

I haven't found any changelog or documentation explaining this change, so it might be an unintentional change. Locally I can reproduce that --timeout=0 is no longer fast. I'm not sure yet if this is a definitive fix, otherwise we might need another workaround.

Checklist

• This PR has adequate test coverage / QA involvement has been duly considered. (trigger-ci for additional test/nightly runs)
• This PR has an associated up-to-date design doc, is a design doc (template), or is sufficiently small to not require a design.
• If this PR evolves an existing $T ⇔ Proto$T mapping (possibly in a backwards-incompatible way), then it is tagged with a T-proto label.
• If this PR will require changes to cloud orchestration or tests, there is a companion cloud PR to account for those changes that is tagged with the release-blocker label (example).
• If this PR includes major user-facing behavior changes, I have pinged the relevant PM to schedule a changelog post.