[BUG] Complete a curl operation that is never scheduled

Add the CHANGELOG entry now that the pull request has a number.

Signed-off-by: thc1006 <84045975+thc1006@users.noreply.github.com>

Author: thc1006

CHANGELOG.md

@@ -30,6 +30,9 @@ Increment the:
 * [BUG] Draw the curl retry jitter from a per thread generator instead of one
   shared across HTTP client threads
   ([#4399](https://github.com/open-telemetry/opentelemetry-cpp/pull/4399))
+* [BUG] Finish a curl operation that never gets scheduled, instead of leaving
+  FinishSession blocked forever
+  ([#4395](https://github.com/open-telemetry/opentelemetry-cpp/pull/4395))
 * [CODE HEALTH] Enable clang-tidy `modernize-deprecated-headers` and replace
   deprecated C headers (`stdint.h`, `stddef.h`, `stdlib.h`, `string.h`,
   `stdio.h`, `ctype.h`, `limits.h`, `assert.h`) with their C++ equivalents