[basic.def.odr] Fix example to perform the lvalue-to-rvalue conversion

outside the conditional expression, as intended.

Author: zygoloid

source/basic.tex

@@ -279,7 +279,7 @@
 \tcode{S::x} subexpression.
 \begin{codeblock}
 struct S { static const int x = 0; };
-int f(const int &r);
+const int &f(const int &r);
 int n = b ? (1, S::x)  // \tcode{S::x} is not odr-used here
           : f(S::x);   // \tcode{S::x} is odr-used here, so
                        // a definition is required