Dependabot: allow 10 open PRs for general updates

[anoadragon453]

Raises the default number of allowed open @dependabot PR updates from 5 to 10. Note that security updates have a non-configurable, separate limit of 10.

Option documentation:
https://docs.github.com/en/code-security/dependabot/working-with-dependabot/dependabot-options-reference#open-pull-requests-limit-

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
  • End with either a period (.) or an exclamation mark (!).
  • Start with a capital letter.
  • Feel free to credit yourself, by adding a sentence "Contributed by @github_username." or "Contributed by [Your Name]." to the end of the entry.
• Code style is correct (run the linters)

[reivilibre]

thanks (note: as agreed in the monday meeting)