UI improvements in the email domain discovery feature

[asekawa]

Describe the issue:

1.The user should notify that the email as a username feature has to be configured to tryout the end-to- end flow sucessfully

2.Better to provide an example of the expected email.domain for better clarity

How to reproduce:

Expected behavior:

Environment information (Please complete the following information; remove any unnecessary fields) :

• Product Version: [e.g., IS 5.10.0, IS 5.9.0]
• OS: [e.g., Windows, Linux, Mac]
• Database: [e.g., MySQL, H2]
• Userstore: [e.g., LDAP, JDBC]

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Related issues:

Suggested labels:

[Rashmini]

Fixed with wso2/identity-apps#4466