fix: unknown attribute "string_type" (#26947) (#26950)

(cherry picked from commit 6aed9e26acaf266f7260adab16656d554c6bb022)

Co-authored-by: Ankush Menat <ankush@iwebnotes.com>
diff --git a/erpnext/hr/doctype/attendance/attendance.py b/erpnext/hr/doctype/attendance/attendance.py
index f79f0fe..c1a7c8f 100644
--- a/erpnext/hr/doctype/attendance/attendance.py
+++ b/erpnext/hr/doctype/attendance/attendance.py
@@ -135,7 +135,7 @@
 def mark_bulk_attendance(data):
 	import json
 	from pprint import pprint
-	if isinstance(data, frappe.string_types):
+	if isinstance(data, str):
 		data = json.loads(data)
 	data = frappe._dict(data)
 	company = frappe.get_value('Employee', data.employee, 'company')