Update P2C testing to use @example.com for email examples

Author: wjdp

features/pay-to-card/testing.mdx

@@ -72,7 +72,7 @@ A returning user will already have their card and other details saved.
 
 To simulate a returning recipient experience in the Playground environment, append `+repeat` to the username part of your email address.
 
-For example, if your email is `user.name@mailserver.com`, use `user.name+repeat@mailserver.com`.
+For example, if your email is `user@example.com`, use `user+repeat@example.com`.
 
 You will still receive the one-time code in your usual inbox.