Remove now unecessary fallback to json_decode

[alganet]

Since PHP 8.3, we don't need that fallback anymore. Now that the library is set to a minimum PHP 8.5, we can safely remove it.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.11%. Comparing base (b69beb1) to head (42cbbf3).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1637      +/-   ##
============================================
+ Coverage     98.03%   98.11%   +0.08%     
+ Complexity      961      960       -1     
============================================
  Files           197      197              
  Lines          2234     2231       -3     
============================================
- Hits           2190     2189       -1     
+ Misses           44       42       -2     

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[alganet]

Thanks! Waiting for #1636 so the CI will run cleaner on main.