ci(mergify): upgrade configuration to current format

[mergify]

No more deprecated fields are being used in your Mergify configuration, this pull request will be closed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.85%. Comparing base (a6f8195) to head (f6b27ed).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3060   +/-   ##
=======================================
  Coverage   89.85%   89.85%           
=======================================
  Files          29       29           
  Lines       32131    32131           
  Branches     5765     5765           
=======================================
  Hits        28871    28871           
  Misses       1859     1859           
  Partials     1401     1401           

Flag	Coverage Δ
c-tests	86.69% <ø> (ø)
lwt-tests	80.78% <ø> (ø)
python-c-tests	89.05% <ø> (ø)
python-tests	98.98% <ø> (ø)

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