fix(group_theory/nielsen_schreier): fix typo (#18483)

ChrisHughes24 · ChrisHughes24 · commit 1bda4fc53de6 · 2023-02-22T18:57:02.000Z
diff --git a/src/group_theory/nielsen_schreier.lean b/src/group_theory/nielsen_schreier.lean
@@ -88,7 +88,7 @@ lemma ext_functor {G} [groupoid.{v} G] [is_free_groupoid G] {X : Type v} [group
 let ⟨_, _, u⟩ := @unique_lift G _ _ X _ (λ (a b : generators G) (e : a ⟶ b), g.map (of e)) in
 trans (u _ h) (u _ (λ _ _ _, rfl)).symm
 
-/-- An action groupoid over a free froup is free. More generally, one could show that the groupoid
+/-- An action groupoid over a free group is free. More generally, one could show that the groupoid
 of elements over a free groupoid is free, but this version is easier to prove and suffices for our
 purposes.
 
