Fix CA2000 Warning: Properly Dispose of RegistryKey in Example Code.

[shethaadit]

Summary

This PR updates the example code for querying the .NET Framework version in the registry to resolve a CA2000 code analysis warning.

Changes:

• Introduced a using block for the RegistryKey.OpenBaseKey call to ensure proper disposal of the base key.
• Modified nested using blocks to manage the lifecycle of both baseKey and ndpKey in a resource-safe manner.
• Ensures compliance with best practices for resource management in .NET.

Impact:

These changes prevent potential resource leaks and improve the robustness of the provided example code. This is particularly relevant for developers following the documentation to avoid introducing subtle bugs in their applications.

Fixes #44083

[gewarren]

Thanks @shethaadit