ci(Mergify): configuration update

[jacobweinstock]

This change has been made by @jacobweinstock from the Mergify config editor.

[jacobweinstock]

this is to fix, https://github.com/bmc-toolbox/bmclib/pull/422/checks?check_run_id=52279132694

Configuration not compatible with a branch protection setting
The branch protection setting Require branches to be up to date before merging is not compatible with draft PR checks. To keep this branch protection enabled, update your Mergify configuration to enable in-place checks: set merge_queue.max_parallel_checks: 1, set every queue rule batch_size: 1, and avoid two-step CI (make merge_conditions identical to queue_conditions). Otherwise, disable this branch protection.

[jacobweinstock]

closing in favor of #425