CI: consider running fetch-configlet job on a schedule

[ee7]

The fetch-configlet job currently only runs automatically when a fetch-configlet script is changed:

configlet/.github/workflows/fetch-configlet.yml

Lines 3 to 10 in 2630458

	on:
	push:
	paths:
	- scripts/fetch-configlet*
	pull_request:
	paths:
	- scripts/fetch-configlet*
	workflow_dispatch:

But this means that it could take a while to find out about problems due to e.g. breaking changes from a PowerShell version update (#839).

We could:

1. Do nothing.
2. Make the job run periodically.
3. Make the job run unconditionally.

This issue is for option 2, which seems reasonable.