[FIX] ciso646 is deprecated

[eseiler]

gcc-mirror/gcc@5c34f02#diff-62a23e8a5ebebf0690390ca9d369d4a79f6e85ffc00712f521ebcd0206a62dbc

#if __cplusplus >= 202002L && ! _GLIBCXX_USE_DEPRECATED
#  error "<ciso646> is not a standard header in C++20, use <version> to detect implementation-specific macros"
#elif __cplusplus >= 201703L && defined __DEPRECATED
#  pragma GCC diagnostic push
#  pragma GCC diagnostic ignored "-Wc++23-extensions"
#  warning "<ciso646> is deprecated in C++17, use <version> to detect implementation-specific macros"
#  pragma GCC diagnostic pop
#endif

Errors on nightly gcc trunk builds

<version> makes both __GLIBCXX__ and _LIBCPP_VERSION available

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.13%. Comparing base (77db997) to head (5a373da).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3302   +/-   ##
=======================================
  Coverage   98.13%   98.13%           
=======================================
  Files         271      271           
  Lines       11948    11948           
  Branches      104      104           
=======================================
  Hits        11725    11725           
  Misses        223      223           

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