Add changelog entry.

Signed-off-by: Charles Korn <charles.korn@grafana.com>

CHANGELOG.md

@@ -11,6 +11,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 ## Unreleased
 
 ### Fixed
+- [#117](https://github.com/thanos-io/objstore/pull/117) Metrics: Fix `objstore_bucket_operation_failures_total` incorrectly incremented if context is cancelled while reading object contents.
 - [#115](https://github.com/thanos-io/objstore/pull/115) GCS: Fix creation of bucket with GRPC connections. Also update storage client to `v1.40.0`.
 - [#102](https://github.com/thanos-io/objstore/pull/102) Azure: bump azblob sdk to get concurrency fixes.
 - [#33](https://github.com/thanos-io/objstore/pull/33) Tracing: Add `ContextWithTracer()` to inject the tracer into the context.