unicode_chars.rs is outdated again

[est31]

src/libsyntax/parse/lexer/unicode_chars.rs contains a list of confusable characters (see #25957). Its comments mention that it bases on a document. Of this document, a newer revision has been published (link). We should update unicode_chars.rs to include the newly listed confusables as well.

In the last update, in #43629, I've suggested manually going through the list. But maybe we can find a way to isolate the characters that are special to us and autogenerate the remaining list?