"Anti test: Detecting UDP leaks of DNS lookups with the firewall leak detector" fails on Jenkins

Originally created by @intrigeri on #16351 (Redmine)

It started failing a few days ago. I suspect that’s caused by the DDoS mitigations but let’s investigate. Possible outcomes: mark the test as fragile, fix the infra, call this an actual bug in Tails or its test suite.

Related issues

• Blocks tails/tails#13241