[expr.unary.op] remove redundant value category wording

Author: Eisenwave

source/expressions.tex

@@ -4650,7 +4650,6 @@
 \indextext{expression!pointer-to-member constant}%
 The operand of the unary \tcode{\&} operator
 shall be an lvalue of some type \tcode{T}.
-The result is a prvalue.
 \begin{itemize}
 \item
 If the operand is a \grammarterm{qualified-id} naming a non-static or variant member \tcode{m}