chore(deps): update akhileshns/heroku-deploy action to v3.15.15

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
akhileshns/heroku-deploy	action	minor	v3.12.14 → v3.15.15

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Release Notes

akhileshns/heroku-deploy (akhileshns/heroku-deploy)

v3.15.15

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• Bumped Node version to 24 (courtesy of @​papotte)

v3.14.15

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• Fix stack issue (courtesy of @​sstepanchuk)
• Add dotenv dependency (courtesy of @​sstepanchuk)
• Update documentation to more precisely mention that the heroku cli must be installed

v3.13.15

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Updated node version to "node20" (as "node18" is not supported by GitHub Actions)

v3.13.14

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Updated node version from 16 to 18 (as 16 is causing problems due to deprecation)

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.50%. Comparing base (4e44a29) to head (30cd06c).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #613   +/-   ##
=======================================
  Coverage   92.50%   92.50%           
=======================================
  Files           4        4           
  Lines          80       80           
  Branches       23       23           
=======================================
  Hits           74       74           
  Misses          6        6           

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