docs: Fix link that has drifted (sendgrid#1052)

Author: jonathanberger

README.md

@@ -98,7 +98,7 @@ print(response.body)
 print(response.headers)
 ```
 
-The `Mail` constructor creates a [personalization object](https://sendgrid.com/docs/Classroom/Send/v3_Mail_Send/personalizations.html) for you. [Here](examples/helpers/mail_example.py#L16) is an example of how to add it.
+The `Mail` constructor creates a [personalization object](https://sendgrid.com/docs/Classroom/Send/v3_Mail_Send/personalizations.html) for you. [Here](examples/helpers/mail_example.py#L28) is an example of how to add it.
 
 ### Without Mail Helper Class