Fix tests for 8.6

[Art4]

PHP 8.6 will start to output more error details on decoding JSON. e.g. Syntax error will become Syntax error near location 1:12, so the tests for PHP 8.6 fails at the moment.

This PR will fix this.

See https://php.watch/versions/8.6/json_decode-error-position

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.52%. Comparing base (00d823f) to head (f67a8fc).
⚠️ Report is 8 commits behind head on v2.x.

Additional details and impacted files

@@            Coverage Diff            @@
##               v2.x     #460   +/-   ##
=========================================
  Coverage     98.52%   98.52%           
  Complexity      661      661           
=========================================
  Files            29       29           
  Lines          2031     2033    +2     
=========================================
+ Hits           2001     2003    +2     
  Misses           30       30           

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