Add a changelog entry for the otlp cert path property (#2600)

Author: jkwatson

CHANGELOG.md

@@ -71,6 +71,8 @@ should acquire the fallback from the default resource, rather than having it con
 
 - The `opentelemetry-sdk-extension-autoconfigure` module will now additionally register the auto-configured
 SDK as the instance of `GlobalOpenTelemetry` when used.
+- The `opentelemetry-sdk-extension-autoconfigure` module now supports the `otel.exporter.otlp.certificate` configuration
+property for specifying a path to a trusted certificate for the OTLP exporters.
 
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