fix typos

quarto/ODEs/differential_equations.qmd

@@ -260,7 +260,7 @@ This very clearly shows the sharp dependence on the value of $b$; below some lev
 
 The function `recovered` is of two variables returning a single value. In subsequent sections we will see a few $3$-dimensional plots that are common for such functions, here we skip ahead and show how to visualize multiple function plots at once using "`z`" values in a graph.
 
-::: {#fig-recoverd-over-various-k-values}
+::: {#fig-recovered-over-various-k-values}
 ```{julia}
 #| hold: true
 k, ks = 0.1, 0.2:0.1:0.9  # first `k` and then the rest