Apply fixes from PR #960 and #959 to Japanese and Korean documentation

[Copilot]

This PR applies the documentation fixes from pull requests #960 and #959 to the Japanese and Korean language documentation to maintain consistency across all supported languages.

Changes Applied

From PR #960 (Streaming Hub fixes)

Applied to Japanese and Korean versions of streaminghub/getting-started.md:

1. Method name correction: Fixed interface method name from OnSendMessage to OnMessage

   - void OnSendMessage(string userName, string message);
   + void OnMessage(string userName, string message);

2. ConnectionId API usage: Fixed incorrect Context.ConnectionId usage to proper ConnectionId.toString()

   - room.All.OnLeave(Context.ConnectionId);
   + room.All.OnLeave(ConnectionId.toString());

From PR #959 (Extensibility typo fix)

Applied to Japanese version of filter/extensibility.md:

1. Spelling correction: Fixed typo in class inheritance

   - class SampleFilterAttribute : Attrubute, IMagicOnionFilterFactory<IMagicOnionServiceFilter>
   + class SampleFilterAttribute : Attribute, IMagicOnionFilterFactory<IMagicOnionServiceFilter>

Note: The Korean extensibility documentation already had the correct spelling.

Files Modified

• docs/i18n/ja/docusaurus-plugin-content-docs/current/streaminghub/getting-started.md
• docs/i18n/ko/docusaurus-plugin-content-docs/current/streaminghub/getting-started.md
• docs/i18n/ja/docusaurus-plugin-content-docs/current/filter/extensibility.md

These changes ensure that all language versions of the documentation (English, Japanese, Korean) are now consistent and contain the same corrections.

Fixes #961.

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