[dcl.init] Fix "operand of a comma" -> "operand of a comma expression"

Author: Stefanus Du Toit

source/declarators.tex

@@ -2630,7 +2630,7 @@
 type~(\ref{basic.fundamental}) is produced by the evaluation of:
 \begin{itemize}
 \item the second or third operand of a conditional expression~(\ref{expr.cond}),
-\item the right operand of a comma~(\ref{expr.comma}),
+\item the right operand of a comma expression~(\ref{expr.comma}),
 \item the operand of a cast or conversion to an unsigned narrow character
 type~(\ref{conv.integral}, \ref{expr.type.conv}, \ref{expr.static.cast},
 \ref{expr.cast}), or