Update dependency slack to v4.15.0

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
slack	orb	minor	4.13.3 -> 4.15.0

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Configuration

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.24%. Comparing base (9b28ae1) to head (31f7dd3).
Report is 493 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9341   +/-   ##
=======================================
  Coverage   65.24%   65.24%           
=======================================
  Files         624      624           
  Lines       59623    59623           
  Branches     6636     6636           
=======================================
  Hits        38899    38899           
  Misses      20724    20724           

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