fix: Replace \textbf with \cat

Author: ktgw0316

src/content/3.14/lawvere-theories.tex

@@ -614,7 +614,7 @@ \section{Challenges}
         binary operations can be generated using the corresponding Kleisli
         arrows.
   \item
-        \textbf{FinSet} is a subcategory of $\Set$ and there is a
+        $\cat{FinSet}$ is a subcategory of $\Set$ and there is a
         functor that embeds it in $\Set$. Any functor on $\Set$
         can be restricted to $\cat{FinSet}$. Show that a finitary functor is
         the left Kan extension of its own restriction.