Fix typo in algebra

Thanks to Et
https://stacks.math.columbia.edu/tag/05D5#comment-8338

algebra.tex

@@ -37946,10 +37946,11 @@ \section{Smoothness and differentials}
 of $R$-algebras we can fill in the dotted arrow by some $R$-algebra
 map $\tau : S \to P/J^n$ making the diagram commute. This induces an
 $R$-algebra map $\overline{\tau} : S/I^n \to P/J^n$ which is equal to
-$\sigma_{n - 1}$ modulo $J^n$. By construction the map $\Psi_n$ is surjective
+$\sigma_{n - 1}$ modulo $J^{n - 1}$. By construction the map $\Psi_n$
+is surjective
 and now $\overline{\tau} \circ \Psi_n$ is an $R$-algebra endomorphism
 of $P/J^n$ which maps $x_i$ to $x_i + \delta_{i, n}$ with
-$\delta_{i, n} \in J^{n -1}/J^n$. It follows that $\Psi_n$ is an
+$\delta_{i, n} \in J^{n - 1}/J^n$. It follows that $\Psi_n$ is an
 isomorphism and hence it has an inverse $\sigma_n$.
 This proves the lemma.
 \end{proof}