[internal] Polish renovate schedule

[oliviertassinari]

Since #46483 we have the setting shared, but I think we are better of making the schedule specific to each repository

Looking at the history, we haven't been consistent enough to run this update: https://github.com/mui/material-ui/pulls?q=is%3Apr+%22Lock+file+maintenance%22+is%3Aclosed. Which seems to be why we have so many of those: https://github.com/mui/material-ui/security/dependabot.

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[oliviertassinari]

I'm merging, it's a simple one, each time renovate update the deps of a repository, it does it with prConcurrentLimit = 30. But:

• In CircleCI, all our GitHub repositories uses the same Circle CI org, on average a PR creates 5 CircleCI tasks. CircleCI has a maximum concurrency of 80. So one repository is enough to starve CircleCI.
• Netlify, all our GitHub repositories uses the same Netlify org. Netlify has a maximum concurrency of 5. So one repository is enough to starve Netlify.

So we need each repository to set a different schedule.

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Also, it says that the natural language syntax is deprecated https://docs.renovatebot.com/configuration-options/#schedule, it should use the cron on:

Config support questions are no longer accepted for Later syntax problems - you will be recommended to use Cron instead