Remove unused forward declaration

src/lib/extractorutil.h

@@ -11,7 +11,6 @@
 namespace KItinerary {
 
 class Flight;
-class PostalAddress;
 
 /** Data extraction utility functions. */
 namespace ExtractorUtil

src/lib/stringutil.h

@@ -6,7 +6,6 @@
 
 #pragma once
 
-class QChar;
 class QString;
 class QStringView;