CWG3086 Destringizing should consider all sorts of encoding-prefixes

Fixes NB US 60-110 (C++26 CD).

Author: eisenwave

source/preprocessor.tex

@@ -2481,12 +2481,12 @@
 \indextext{operator!pragma|see{macro, pragma operator}}
 
 \pnum
-A unary operator expression of the form:
+A unary operator expression of the form
 \begin{ncbnf}
 \terminal{_Pragma} \terminal{(} string-literal \terminal{)}
 \end{ncbnf}
 is processed as follows: The \grammarterm{string-literal} is \defnx{destringized}{destringization}
-by deleting the \tcode{L} prefix, if present, deleting the leading and trailing
+by deleting any \grammarterm{encoding-prefix}, deleting the leading and trailing
 double-quotes, replacing each escape sequence \tcode{\textbackslash"} by a double-quote, and
 replacing each escape sequence \tcode{\textbackslash\textbackslash} by a single
 backslash. The resulting sequence of characters is processed through translation phase 3