Revert "Fix DisposeAsync pattern: remove incorrect Dispose(false) call"

[gewarren]

Reverts #50900
Fixes #51019.

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Internal previews

📄 File	🔗 Preview link
docs/standard/garbage-collection/implementing-disposeasync.md	Implement a DisposeAsync method

[Copilot]

Pull request overview

This PR reverts a previous change (PR #50900) that incorrectly removed the Dispose(disposing: false) call from the DisposeAsync method. The original removal broke the dispose pattern by preventing unmanaged resources in derived classes from being properly disposed when using async disposal. This revert restores the correct implementation pattern.

Changes:

• Restores Dispose(disposing: false) call in DisposeAsync() method in the code example
• Adds documentation explaining why Dispose(false) must be called in the async dispose pattern
• Adds a NOTE section clarifying the difference between calling Dispose(false) in DisposeAsync vs Dispose(true) in Dispose

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
docs/standard/garbage-collection/snippets/dispose-async/ExampleConjunctiveDisposable.cs	Restores the Dispose(disposing: false) call in the DisposeAsync method to ensure unmanaged resources are properly disposed
docs/standard/garbage-collection/implementing-disposeasync.md	Adds documentation explaining the correct async dispose pattern, including the rationale for calling Dispose(false) instead of Dispose(true)

[Copilot]

The example code in line 45 should use .ConfigureAwait(false) after DisposeAsyncCore(). The code snippet shows await DisposeAsyncCore(); but the correct pattern demonstrated throughout the rest of the document and in the actual implementation file uses await DisposeAsyncCore().ConfigureAwait(false); to avoid capturing the synchronization context unnecessarily.

Suggested change

	await DisposeAsyncCore();
	await DisposeAsyncCore().ConfigureAwait(false);