Remove redundant Fl_Group::clear() from ~Fl_Scroll()

Fl_Group::clear() is called in Fl_Group's d'tor anyway.

Technically we don't need to remove hscrollbar and scrollbar because
they are destroyed (and thus removed from Fl_Group) before Fl_Group's
d'tor is executed but this is left for clarity and to guarantee the
order (see comment).

src/Fl_Scroll.cxx

@@ -1,7 +1,7 @@
 //
 // Fl_Scroll widget for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2022 by Bill Spitzak and others.
+// Copyright 1998-2025 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -41,7 +41,6 @@ void Fl_Scroll::clear() {
 Fl_Scroll::~Fl_Scroll() {
   remove(hscrollbar); // remove last child first
   remove(scrollbar);
-  Fl_Group::clear();
 }
 
 /** Ensure the scrollbars are the last children.