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Improve notice's wording, to clarify that code is still under Apache 2.0 license, but is no longer maintained here.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

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[Copilot]

Pull request overview

This PR improves the README notice to clarify the repository's maintenance status and licensing. The key change is emphasizing that while the repository is no longer actively maintained, the existing code remains available under the Apache 2.0 license.

Key changes:

• Updated notice title from "no longer open source" to "no longer maintained" for accuracy
• Added explicit clarification that existing code can be used under Apache 2.0 license
• Clarified that the private repository link is for Wise employees only

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[Copilot]

[nitpick] The phrasing "For continued development and access (Wise employees only):" followed by "The codebase has moved to a private repository accessible to authorized Wise personnel:" is redundant. Consider consolidating these lines for better clarity and conciseness. For example:

> **For Wise employees only:**
> The codebase has moved to a private repository for continued development and access:

This reduces repetition while maintaining the same information.

Suggested change

	> **For continued development and access (Wise employees only):**
	> The codebase has moved to a private repository accessible to authorized Wise personnel:
	> **For Wise employees only:**
	> The codebase has moved to a private repository for continued development and access: