fix: update LaunchDarkly.EventSource to 5.3.2 for MAUI Android SSE stall

[tanderson-ld]

Related issues

• Fix PR in dotnet-eventsource: fix: SSE streaming stall on MAUI Android (SDK-2755) dotnet-eventsource#124
• 5.3.2 release notes: https://github.com/launchdarkly/dotnet-eventsource/releases/tag/5.3.2

Describe the solution you've provided

Bumps LaunchDarkly.EventSource from 5.3.1 to 5.3.2 in LaunchDarkly.ClientSdk. The 5.3.2 release increases the SSE read buffer from 1024 to 8192 bytes to bypass a stall in Xamarin.Android.Net.AndroidMessageHandler's BufferedStream small-count code path, which caused MAUI Android consumers' SSE reads to block for ~60 s waiting for the next server keepalive.

The fix was validated end-to-end with a new sse-contract-tests payload-size sweep run against a .NET-for-Android build of the SSE test service in an Android emulator; the sweep flags every regression to a sub-4096-byte buffer.

Describe alternatives you've considered

• Working around the stall in-repo (e.g., swapping out AndroidMessageHandler for a different HTTP handler) was rejected as riskier than adjusting the buffer size at the SSE layer.
• The ServerSdk consumer of LaunchDarkly.EventSource is out of scope for this PR: the stall is Android-only, so bumping ServerSdk would be pure hygiene rather than a fix.

Additional context

• No API changes; single-line PackageReference version bump.
• Companion to previously merged fix: treat unknown/constrained network access as connected #323, which addressed the network-connectivity side of the same customer-reported symptom.
• Verified locally that LaunchDarkly.ClientSdk builds cleanly against 5.3.2 for both netstandard2.0 and net8.0-android.

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Note

Overview
Bumps LaunchDarkly.EventSource from 5.3.1 to 5.3.2 in LaunchDarkly.ClientSdk only (no API or source changes).

The newer EventSource release increases the SSE read buffer (1024 → 8192 bytes) so MAUI Android clients avoid long (~60s) stalls when AndroidMessageHandler’s buffered stream blocks on small reads until the next keepalive. LaunchDarkly.ServerSdk is intentionally left on 5.3.1 because the issue is Android-specific.

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