[basic.lookup.classref] Use code font for ~.

Author: zygoloid

source/basic.tex

@@ -2087,7 +2087,7 @@
 \grammarterm{postfix-expression}.
 
 \pnum
-If the \grammarterm{unqualified-id} is \grammarterm{\tilde{}type-name}, the
+If the \grammarterm{unqualified-id} is \tcode{\~}\grammarterm{type-name}, the
 \grammarterm{type-name} is looked up in the context of the entire
 \grammarterm{postfix-expression}. If the type \tcode{T} of the object
 expression is of a class type \tcode{C}, the \grammarterm{type-name} is