Add CHANGELOG entry for ProbabilitySampler ot.th revision

Author: yuanyuanzhao3

CHANGELOG.md

@@ -11,6 +11,9 @@ release.
 
 ### Traces
 
+- Revise `ProbabilitySampler` specification to avoid or erase the `ot.th` key
+  when trace ID randomness and an explicit `rv` value are not available. ([#5039](https://github.com/open-telemetry/opentelemetry-specification/pull/5039))
+
 ### Metrics
 
 ### Logs

specification/trace/sdk.md

@@ -36,8 +36,8 @@ weight: 3
       - [Requirements for `TraceIdRatioBased` sampler algorithm](#requirements-for-traceidratiobased-sampler-algorithm)
       - [Compatibility warnings for `TraceIdRatioBased` sampler](#compatibility-warnings-for-traceidratiobased-sampler)
     + [ProbabilitySampler](#probabilitysampler)
-      - [`ProbabilitySampler` sampler configuration](#probabilitysampler-sampler-configuration)
-      - [`ProbabilitySampler` sampler algorithm](#probabilitysampler-sampler-algorithm)
+      - [`ProbabilitySampler` configuration](#probabilitysampler-configuration)
+      - [`ProbabilitySampler` sampling algorithm](#probabilitysampler-sampling-algorithm)
       - [Compatibility warnings for `ProbabilitySampler`](#compatibility-warnings-for-probabilitysampler)
     + [ParentBased](#parentbased)
     + [JaegerRemoteSampler](#jaegerremotesampler)