fix(email): remove hardcoded subject from SendGrid template

- Remove 'subject' field from SendGrid template data
- This change allows the email subject to be dynamically set in the template

Author: fulleni

lib/src/email_sendgrid.dart

@@ -50,7 +50,6 @@ class EmailSendGrid implements EmailClient {
         },
       ],
       'from': {'email': senderEmail},
-      'subject': templateData['otp_code'],
       'template_id': templateId,
     };