Chapter 12: fix a minor inconsistency

See #176. Originally Harry “only” applauded two people. Instead, guess that
when talking about Zabini, the point is that he meant to start applauding
Slytherins, but only managed to applaud one before Sorting ended.

chapters/hpmor-chapter-012.tex

@@ -66,7 +66,7 @@ \chapter{Impulse Control}
 
 Harry applauded Zabini too, ignoring the odd looks he was getting from everyone including Zabini.
 
-No other name was called out after that, and Harry realised that “Zabini, Blaise” did sound close to the end of the alphabet. Great, so now he’d \emph{only} applauded Zabini…Oh well.
+No other name was called out after that, and Harry realised that “Zabini, Blaise” did sound close to the end of the alphabet. Great, so now the \emph{only} Slytherin he’d applauded was Zabini…Oh well.
 
 Dumbledore got up again and began heading towards the podium. Apparently they were about to be treated to a speech—