docs: Note rejected SDK key retry in the initialization matrix row

[kinyoklion]

LaunchDarkly .NET SDK 8.17.0 made a rejected SDK key (401/403 and other 4xx) retryable, so the data source no longer reaches Off for it. The README matrix still said InitializeAsync waits until the client becomes ready "or fails permanently", which is no longer true for a rejected key.

• Initialization row: now ⚠️. It notes the SDK 8.17.0 behavior: without a cancellation token, InitializeAsync can wait indefinitely. It links the provider-side tracking PR #71 (start wait).
• Asynchronous Initialization: the SDK's default StartWaitTime is 10 seconds (ConfigurationBuilder.DefaultStartWaitTime). The README said 5.

Details

Requirements

• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

Related issues

#71

Describe the solution you've provided

The provider references LaunchDarkly.ServerSdk [8.1.0,9.0), so new installs resolve to 8.17.x and get the retry behavior. 8.17.0 release notes: "DataSourceState.Off no longer indicates a rejected SDK key. Off is now reached only by explicit shutdown."

main was merged in after #72 (cancellation token) landed. The row now keeps #72's cancellation wording and no longer links #72 as a gap.

Additional context

#71 also edits the Initialization row. Whichever merges second will need a small README conflict fix.

Found in the weekly OpenFeature provider audit. Docs-only change.

Link to Devin session: https://app.devin.ai/sessions/2a67f9d291bc4417bb40f632c191b44f
Open in Devin Desktop: https://app.devin.ai/desktop/session/2a67f9d291bc4417bb40f632c191b44f?variant=devin
Requested by: @kinyoklion

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Note

Overview
Updates the README Initialization feature matrix row to partial (⚠️) and revises how InitializeAsync behaves with LaunchDarkly .NET SDK 8.17.0+: a rejected SDK key is retried instead of failing permanently, so without a SetProviderAsync cancellation token initialization can wait indefinitely. The row now says init waits until ready or shutdown (not permanent failure) and links provider follow-up #71.

In Asynchronous Initialization, the documented default constructor blocking wait is corrected from 5 to 10 seconds to match ConfigurationBuilder.DefaultStartWaitTime.

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