Fix: Do not use deprecated --diff-format option

[localheinz]

This pull request

• stops using the deprecated --diff-format option

[codecov]

Codecov Report

Merging #492 (09171f0) into main (8b33d2e) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main     #492   +/-   ##
=========================================
  Coverage     97.31%   97.31%           
  Complexity       52       52           
=========================================
  Files             6        6           
  Lines           149      149           
=========================================
  Hits            145      145           
  Misses            4        4           

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