design/tpl: Corrected conjunction/disjunction index placement

They were incorrectly placed at the quantifiers.

design/tpl/sec/notation.tex

@@ -37,10 +37,14 @@ We use $\implies$ in place of $\rightarrow$ for implication,
 We further use $\equiv$ in place of $\leftrightarrow$ to represent material
   equivalence.
 
+\indexsym\logand{conjunction}
+\index{conjunction (\ensuremath{\logand})}
 \begin{definition}[Logical Conjunction]
   $p,q \infer (p\logand q)$.
 \end{definition}
 
+\indexsym\logor{disjunction}
+\index{disjunction (\ensuremath{\logor})}
 \begin{definition}[Logical Disjunction]
   $p \infer (p\logor q)$ and $q \infer (p\logor q)$.
 \end{definition}