chore: update LaunchDarkly AI SDK dependencies to latest versions

[kinyoklion]

Summary

Updates all LaunchDarkly SDK dependencies across all example projects to their latest stable versions:

• launchdarkly-server-sdk-ai: >=0.20.0 / >=1.0.0,<2.0.0 → >=1.1.0 / >=1.1.0,<2.0.0
• launchdarkly-server-sdk-ai-openai: >=0.5.0 → >=0.7.0
• launchdarkly-server-sdk-ai-langchain: >=0.6.0 → >=0.8.0
• launchdarkly-observability: >=0.1.0 → >=1.2.4

Verified SDK initializes successfully with the updated versions. No deprecated API usage found in any example code — all examples already use the current API patterns.

Link to Devin session: https://app.devin.ai/sessions/2fe1ed1c455149ca954690b7c4ef9ed3
Requested by: @kinyoklion

[devin-ai-integration]

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[devin-ai-integration]

Closing — no version bump needed. The existing open >= constraints already resolve to the latest published versions on install, so the example already runs against the current SDKs. Per maintainer guidance we don't raise a minimum that's already satisfied.