Issue #3464418: Working on the security advisory comments.

config/schema/abstract_email_validation.schema.yml

@@ -12,6 +12,7 @@ abstract_email_validation.settings:
     custom_error_message:
       type: text
       label: 'Custom Error Message'
+      translatable: true
     user_registration_form_email_validation:
       type: boolean
       label: 'User Registration Form Email Validation'