fix: do not cache value while creating item group, in setup wizard it will raise link validation error (#18992)

diff --git a/erpnext/setup/doctype/item_group/item_group.py b/erpnext/setup/doctype/item_group/item_group.py
index b309b50..5603f17 100644
--- a/erpnext/setup/doctype/item_group/item_group.py
+++ b/erpnext/setup/doctype/item_group/item_group.py
@@ -29,7 +29,7 @@
 		super(ItemGroup, self).validate()
 
 		if not self.parent_item_group and not frappe.flags.in_test:
-			if frappe.db.exists("Item Group", _('All Item Groups'), cache=True):
+			if frappe.db.exists("Item Group", _('All Item Groups')):
 				self.parent_item_group = _('All Item Groups')
 
 		self.make_route()