Fixup: missed formatting for == operator

Author: jensmaurer

source/classes.tex

@@ -6660,7 +6660,7 @@
 \begin{codeblock}
 bool X::operator==(const X&) const;
 \end{codeblock}
-Otherwise, the implicitly-declared == operator function is of the form
+Otherwise, the implicitly-declared \tcode{==} operator function is of the form
 \begin{codeblock}
 friend bool operator==(const X&, const X&);
 \end{codeblock}