Simplify data structures

Do some cleanup.

Change-Id: If40fefbdb646f0eb434539f8306421a40e47a3ee
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

plugins/fossil/annotationhighlighter.cpp

@@ -44,7 +44,7 @@ QString FossilAnnotationHighlighter::changeNumber(const QString &block) const
     QRegularExpressionMatch changesetIdMatch = m_changesetIdPattern.match(block);
     if (changesetIdMatch.hasMatch())
         return changesetIdMatch.captured(1);
-    return QString();
+    return {};
 }
 
 } // namespace Internal