Let Mergify know about the change of branch name

[st3fan]

This patch uses a new regular expression to match both the new and old-style branch names:

• releases/v85.0.0
• releases_v85.0.0

Tested in the Mergify test tool.

[codecov-io]

Codecov Report

Merging #17119 (ff0a3fa) into master (afc8c26) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master   #17119   +/-   ##
=========================================
  Coverage     30.81%   30.81%           
  Complexity     1239     1239           
=========================================
  Files           455      455           
  Lines         18668    18668           
  Branches       2615     2615           
=========================================
  Hits           5753     5753           
  Misses        12453    12453           
  Partials        462      462           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update afc8c26...ff0a3fa. Read the comment docs.