dependabot: enable update grouping

[Ablu]

This was tested on vhost-device successfully [1]. Lets enable it here!

[1] https://github.com/rust-vmm/vhost-device/commit/072fadaaba527133c3466cac90a8c5dd386b1f9e

Suggested-by: Patrick Roy roypat@amazon.co.uk Suggested-by: Stefano Garzarella sgarzare@redhat.com

Requirements

Before submitting your PR, please make sure you addressed the following requirements:

• [x] All commits in this PR are signed (with git commit -s), and the commit message has max 60 characters for the summary and max 75 characters for each description line.
• na All added/changed functionality has a corresponding unit/integration test.
• na All added/changed public-facing functionality has entries in the "Upcoming Release" section of CHANGELOG.md (if no such section exists, please create one).
• na Any newly added unsafe code is properly documented.

[Ablu]

ping!

Does anything speak against doing this?