[PL-50895] Note for cleaning up the user accounts in FirstGen

[saifeemustafaqharness]

Adding the info note:

:::info note
After migrating from FirstGen to NextGen, please clean up the user accounts in FirstGen.
:::

This has been requested by @meenakshi-harness on ticket: https://harness.atlassian.net/browse/PL-50895

Changes will be reflected on the following page:
https://developer.harness.io/docs/continuous-delivery/get-started/upgrading/upgrade-nextgen-cd/#upgrading-to-nextgen-cd

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• Jira/GitHub Issue numbers (if any): ______________________________
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[bot-gitexp-user]

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[saifeemustafaqharness]

@meenakshi-harness @roshnisarangadharan edits added, thanks.
Please approve.

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[saifeemustafaqharness]

@meenakshi-harness Please review and approve. Thanks

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Please check the Execution Link of the Pipeline for the Website Draft URL. This is located in the Preview Step behind the Harness VPN and also is available in #hdh_alerts. E.g Website Draft URL: https://unique-id--harness-developer.netlify.app. Current Draft URL is: https://664c73619c393e06d68d87e5--harness-developer.netlify.app