docs: Update CHANGELOG for HyperClient generic connector support

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Co-Authored-By: Claude <[email protected]>

Author: palindrom615

opentelemetry-http/CHANGELOG.md

@@ -3,6 +3,7 @@
 ## vNext
 
 - Implementation of `Extractor::get_all` for `HeaderExtractor`
+- Support `HttpClient` implementation for `HyperClient<C>` with custom connectors beyond `HttpConnector`, enabling Unix Domain Socket connections and other custom transports
 
 ## 0.30.0