[basic.def.odr] Add missing "potential results of" in one case in the

recursive definition of the set of potential results.

This definition is intended to be a recursive formulation that produces
a set of id-expressions, as explained in the introductory sentence, so
it's clear that we were just missing the recursion in one bullet rather
than trying to terminate the recursion early in this case.

source/basic.tex

@@ -287,7 +287,7 @@
 \grammarterm{id-expression}~(\ref{expr.prim.id}), the set
 contains only \tcode{e}.
 \item If \tcode{e} is a subscripting operation~(\ref{expr.sub}) with
-an array operand, the set contains that operand.
+an array operand, the set contains the potential results of that operand.
 \item If \tcode{e} is a class member access
 expression~(\ref{expr.ref}), the set contains the potential results of
 the object expression.