Fix readme badge

[GoebelL]

Changes in this Pull Request:

• Fix GitHub Actions link in readme badge

Mandatory checks:

• [X] Branch is up to date (latest changes were fetched from the upstream branch before creating this PR)
• [X] Changes were tested manually

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This change is 

[codecov[bot]]

Codecov Report

Merging #1273 (b5e2d4f) into master (f30d41e) will not change coverage. The diff coverage is 90.00%.

@@            Coverage Diff            @@
##             master    #1273   +/-   ##
=========================================
  Coverage     55.47%   55.47%           
  Complexity    14427    14427           
=========================================
  Files          1375     1375           
  Lines         80476    80476           
  Branches       8598     8598           
=========================================
  Hits          44646    44646           
  Misses        33140    33140           
  Partials       2690     2690           

Impacted Files	Coverage Δ
...cm/accountservice/assembler/DiscountAssembler.java	90.24% <90.00%> (ø)