Fix localize Or and Username labels in Authentication Portal and Recovery Portal

[HasiniSama]

Purpose

Fixes wso2/product-is#20936

• The i18nKey variable is set to "Username" instead of "username". The username string does not get translated correctly due to this.
• The string "or" is defined directly without resolving it according to the specific locale. Both of these needs to be fixed.

Checklist

• e2e cypress tests locally verified. (for internal contributers)
• Manual test round performed and verified.
• UX/UI review done on the final implementation.
• Documentation provided. (Add links if there are any)
• Relevant backend changes deployed and verified
• Unit tests provided. (Add links if there are any)
• Integration tests provided. (Add links if there are any)

Security checks

• Followed secure coding standards in http://wso2.com/technical-reports/wso2-secure-engineering-guidelines
• Ran FindSecurityBugs plugin and verified report
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets

[wso2-jenkins-bot]

🦋 Changeset detected

The changes in this PR will be included in the next version bump.

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