refactor: use plain strings for service annotation fixtures

[lukasmetzner]

Preparation for upcoming refactoring.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.26%. Comparing base (ec2103a) to head (7d93160).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1326      +/-   ##
==========================================
- Coverage   71.27%   71.26%   -0.01%     
==========================================
  Files          29       29              
  Lines        2876     2875       -1     
==========================================
- Hits         2050     2049       -1     
  Misses        635      635              
  Partials      191      191              

Flag	Coverage Δ
e2e	44.57% <0.00%> (-0.07%)	⬇️
unit	67.72% <100.00%> (-0.02%)	⬇️

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