[Qt] move SubstituteFonts() above ToolTipToRichTextFilter

- doesn't belong to the ToolTipToRichTextFilter class so move it up

src/qt/guiutil.h

@@ -102,14 +102,13 @@ namespace GUIUtil
     // Open debug.log
     void openDebugLogfile();
 
+    // Replace invalid default fonts with known good ones
+    void SubstituteFonts();
+
     /** Qt event filter that intercepts ToolTipChange events, and replaces the tooltip with a rich text
       representation if needed. This assures that Qt can word-wrap long tooltip messages.
       Tooltips longer than the provided size threshold (in characters) are wrapped.
      */
-
-    // Replace invalid default fonts with known good ones
-    void SubstituteFonts();
-
     class ToolTipToRichTextFilter : public QObject
     {
         Q_OBJECT