Fix type in takeaway slides

lectures/complexity/slides.qmd

@@ -450,7 +450,7 @@ Big-$\mathcal{O}$ informs about large problems, especially for small problems, s
 *never use algorithms if math can do*
 
 :::{.smaller .fragment}
-... and pefer better algorithms if math can't do
+... and prefer better algorithms if math can't do
 :::
 
 ## human time matters