Remove unnecessary WNDPROC casts.

diff --git a/dlls/comctl32/treeview.c b/dlls/comctl32/treeview.c
index 37d100d..cf09fb6 100644
--- a/dlls/comctl32/treeview.c
+++ b/dlls/comctl32/treeview.c
@@ -5399,7 +5399,7 @@
 
     ZeroMemory(&wndClass, sizeof(WNDCLASSA));
     wndClass.style = CS_GLOBALCLASS | CS_DBLCLKS;
-    wndClass.lpfnWndProc = (WNDPROC)TREEVIEW_WindowProc;
+    wndClass.lpfnWndProc = TREEVIEW_WindowProc;
     wndClass.cbClsExtra = 0;
     wndClass.cbWndExtra = sizeof(TREEVIEW_INFO *);