Fix typo reported by @gkurzbach

Co-authored-by: Gerd Kurzbach <Gerd.Kurzbach@esi-group.com>

chapters/classes.tex

@@ -392,7 +392,7 @@ \subsection{Component Variability Prefixes discrete, parameter, constant}\label{
       Medium.specificEnthalpy_pTX(p_start, T_start, X_start) else Medium.h_default
     annotation(Dialog(tab = "Initialization", enable = not use_T_start));
 end PartialLumpedVolume;
-// Cycle for T_start and h_start, but still strucutral since cycle disappears
+// Cycle for T_start and h_start, but still structural since cycle disappears
 // when evaluating use_T_start
 
 // The unexpanded bindings have cycles for both x and y, making them normal parameters