Update content/applications/sales/rental/service_products.rst

Co-authored-by: Felicia Kuan <feku@odoo.com>

Author: meval1006

content/applications/sales/rental/service_products.rst

@@ -230,7 +230,7 @@ A link to the signature request will appear in the chatter of the rental order.
 accessible to the customer via the customer portal or email.
 
 Signing a document from an email link
-------------------------------------
+-------------------------------------
 
 When a customer clicks :guilabel:`Sign document`, a separate page is then revealed, showcasing the
 document to be signed. The customer begins the process by clicking :guilabel:`Click` to start.