Don't use deprecated wxArtProvider::Insert().

Ironically, it was 2.6 compatibility code that was using the function
deprecated after 2.8. In any case, just use the newest name for it.

Closes #13393.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70123 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/artprov.cpp

@@ -407,7 +407,7 @@ bool wxArtProvider::HasNativeProvider()
 
 /* static */ void wxArtProvider::InsertProvider(wxArtProvider *provider)
 {
-    Insert(provider);
+    PushBack(provider);
 }
 
 /* static */ bool wxArtProvider::PopProvider()