[ISO/CS C++2023] Do not use "C++ 20xx" or "ISO C++ 20xx"

[jensmaurer]

Always properly cite older standards.

• Please make this sentence clearer i.e. "C.1 lists the differences between this document and the previous edition (ISO/IEC 14882:2020)."
• General comment for this entire Annex: Use the ISO/IEC document identifier number, not C++ 2020.
• Idem: change to "this document" and "ISO/IEC 14882:2003", respectively
• Comment for the entire annex: please change all references to any previous editions of this document with the document identifier number and the relevant year of publication e.g. "ISO/IEC 14882:2014"