fix: improve drag-and-drop behavior for tab folders, b=closes #11326, p=#11345

Co-authored-by: mr. m <91018726+mr-cheffy@users.noreply.github.com>

prefs/zen/view.yaml

@@ -43,11 +43,8 @@
 - name: zen.view.drag-and-drop.move-over-threshold
   value: 70
 
-- name: zen.view.drag-and-drop.drop-inside-upper-threshold
-  value: 80
-
-- name: zen.view.drag-and-drop.drop-inside-lower-threshold
-  value: 30
+- name: zen.view.drag-and-drop.edge-zone-threshold
+  value: 25
 
 - name: zen.view.context-menu.refresh
   value: false