[expr.const] Add paragraph number for general example

Author: jensmaurer

source/expressions.tex

@@ -7749,6 +7749,8 @@
 would disqualify $E$ from being a core constant expression.
 \end{note}
 \end{itemize}
+
+\pnum
 \begin{example}
 \begin{codeblock}
 int x;                              // not constant