Fix internal return type check with gcov

[iluuu1994]

ZEND_ASSERT() is a no-op with gcov. Move zend_verify_internal_return_type() out of ZEND_ASSERT().

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.24%. Comparing base (6daf99f) to head (6d3a47d).
⚠️ Report is 8 commits behind head on master.

Files with missing lines	Patch %	Lines
Zend/zend_vm_execute.h	86.36%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #21653   +/-   ##
=======================================
  Coverage   69.23%   69.24%           
=======================================
  Files         812      812           
  Lines      296933   296957   +24     
  Branches    84521    84533   +12     
=======================================
+ Hits       205577   205621   +44     
+ Misses      56636    56616   -20     
  Partials    34720    34720           

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