[basic.def] Turn list of examples into a nute

The list of example side effects should neither be deemed normtaive nor
exhaustive (although we will try).  It should be demoted to a note.

Author: AlisdairM

source/basic.tex

@@ -173,14 +173,17 @@
 a redeclaration of $X$
 if another declaration of $X$ is reachable from it\iref{module.reach};
 otherwise, it is a \defnadj{first}{declaration}.
-A declaration may also have effects including:
+
+\begin{note}
+A declaration can also have effects including:
 \begin{itemize}
 \item a static assertion\iref{dcl.pre},
 \item controlling template instantiation\iref{temp.explicit},
 \item guiding template argument deduction for constructors\iref{temp.deduct.guide},
 \item use of attributes\iref{dcl.attr}, and
 \item nothing (in the case of an \grammarterm{empty-declaration}).
 \end{itemize}
+\end{note}
 
 \pnum
 \indextext{declaration!function}%