[module.global.frag] Remove irrelevant note about preprocessor

[module.global.frag] is entirely part of phase 7 of translation,
and it makes no sense to talk of preprocessing directive in the
grammar term *declaration-seq*.  Strike the note rather than try
to turn it into something meaningful.

Author: AlisdairM

source/modules.tex

@@ -587,13 +587,6 @@
     module-keyword \terminal{;} \opt{declaration-seq}
 \end{bnf}
 
-\pnum
-\begin{note}
-Prior to phase 4 of translation,
-only preprocessing directives can appear
-in the \grammarterm{declaration-seq}\iref{cpp.pre}.
-\end{note}
-
 \pnum
 A \grammarterm{global-module-fragment} specifies the contents of the
 \defn{global module fragment} for a module unit.