fix whitespace

Author: atoulme

CHANGELOG.md

@@ -25,7 +25,7 @@ release.
 - Clarify async instrument callback identity.
   ([#2538](https://github.com/open-telemetry/opentelemetry-specification/pull/2538)).
 - Add `process.threads` host metric semantic convention.
-  ([#2705](https://github.com/open-telemetry/opentelemetry-specification/pull/2705)). 
+  ([#2705](https://github.com/open-telemetry/opentelemetry-specification/pull/2705)).
 
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