Improve notice about discontinued maintenance

[xSeagullx]

Context

Improve notice's wording, to clarify that code is still under Apache 2.0 license, but is no longer maintained here.

Point to the new closed source location for Wise employees to simplify transition and avoid broken links.

[platon-github-app-production]

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[Copilot]

Pull request overview

This PR improves the wording of the repository discontinuation notice to more accurately reflect the licensing and maintenance status. The key improvement is clarifying that while the repository is no longer maintained, the code remains available under the Apache 2.0 license.

Key Changes:

• Updated notice from "no longer open source" to "no longer maintained" for accuracy
• Added explicit clarification that existing code can still be used under Apache 2.0 license
• Enhanced messaging for Wise employees about the private repository location

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