Run "Update CI package locks" bot less often

[EwoutH]

This bot is now updated daily, I don't know if that's necessary. It adds a lot of noise in the Git commit history.

Maybe weekly would also be fine? (also good for the environment)

[maartenbreddels]

Yeah, I think that's fine. Ideally, we'd squash multiple of those commits, but I think this is also fine.