play: increase timeout

[oliver-sanders]

Workflows can take substantially longer than 20 seconds to startup.

If this happens the user will see a popup like this:

Causes of slow startup include:

• Complex configuration (number of lines, number of dependencies, etc).
• Python logic run at configure time (i.e. via Jinja2).
• Slow network (scheduler distribution).
• Loaded machine (system load).

This timeout represents the maximum time the user will be kept waiting for a play operation.

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg (and conda-environment.yml if present).
• Tests are included (or explain why tests are not needed).
• Changelog entry included if this is a change that can affect users
• Cylc-Doc pull request opened if required at cylc/cylc-doc/pull/XXXX.
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.