Fix puppeteer timeouts on CI

CI builds often fail because the puppeteer front-end test times out.

Some examples:

• https://gitlab.com/timvisee/send/-/jobs/795248001
• https://gitlab.com/timvisee/send/-/jobs/795250975
• https://gitlab.com/timvisee/send/-/jobs/795265113
• https://gitlab.com/timvisee/send/-/jobs/795269855
• https://gitlab.com/timvisee/send/-/jobs/795270000

Increase this timeout to fix builds.