Revert "Fix crash when deleting all wxTreeListCtrl items with wxGTK3"

This reverts commit 1dd102d741 as it
introduced a crash in the same method when using generic wxDataViewCtrl
implementation, e.g. under MSW, and is not necessary to avoid the crash
with wxGTK3 any longer after the few previous commits.

tests/controls/treelistctrltest.cpp

@@ -39,7 +39,6 @@ private:
         CPPUNIT_TEST( Traversal );
         CPPUNIT_TEST( ItemText );
         CPPUNIT_TEST( ItemCheck );
-        CPPUNIT_TEST( DeleteAll );
     CPPUNIT_TEST_SUITE_END();
 
     // Create the control with the given style.
@@ -56,7 +55,6 @@ private:
     void Traversal();
     void ItemText();
     void ItemCheck();
-    void DeleteAll();
 
 
     // The control itself.
@@ -233,11 +231,4 @@ void TreeListCtrlTestCase::ItemCheck()
                           m_treelist->GetCheckedState(m_code) );
 }
 
-void TreeListCtrlTestCase::DeleteAll()
-{
-    m_treelist->DeleteAllItems();
-
-    CHECK( !m_treelist->GetFirstChild(m_treelist->GetRootItem()).IsOk() );
-}
-
 #endif // wxUSE_TREELISTCTRL