[minor] add the Lead in email account -> append_to field (#10983)

diff --git a/erpnext/hooks.py b/erpnext/hooks.py
index 6d411cd..a6dbd20 100644
--- a/erpnext/hooks.py
+++ b/erpnext/hooks.py
@@ -47,7 +47,7 @@
 update_website_context = "erpnext.shopping_cart.utils.update_website_context"
 my_account_context = "erpnext.shopping_cart.utils.update_my_account_context"
 
-email_append_to = ["Job Applicant", "Opportunity", "Issue"]
+email_append_to = ["Job Applicant", "Lead", "Opportunity", "Issue"]
 
 calendars = ["Task", "Production Order", "Leave Application", "Sales Order", "Holiday List"]