Fix typo

Signed-off-by: zeramorphic <[email protected]>

iii/forcing/03_forcing.tex

@@ -452,7 +452,7 @@ \subsection{???}
     \end{align*}
     Thus \( \dot x^G \in N \) as required.
 \end{proof}
-To prove the generic model theorem, it now suffices to prove the remaining axioms of \( \mathf{ZF} \), which are union, power set, replacement, and separation.
+To prove the generic model theorem, it now suffices to prove the remaining axioms of \( \mathsf{ZF} \), which are union, power set, replacement, and separation.
 We can prove the axiom of union now.
 \begin{lemma}
     Suppose \( M \) is a transitive model of \( \mathsf{ZF} \), \( \mathbb P \in M \) is a forcing poset, and \( G \subseteq \mathbb P \) is such that \( \Bbbone \in G \).