[CHORE] Say what recordCompletion returns in the comment that describes it

The sentence about the return value went in as a second comment stacked under the
block that was already there, which leaves one declaration carrying two doc comments
and Doxygen reading only the last of them. It belongs in the block.

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

Author: thc1006

exporters/elasticsearch/src/es_log_record_exporter.cc

@@ -230,8 +230,9 @@ class ResponseHandler : public http_client::EventHandler
   /**
    * Record the outcome of the request, first writer wins, then release any waiter. Keeping the
    * first outcome means a session destroyed after a successful response does not overwrite it.
+   *
+   * @return whether this call is the one that decided the outcome
    */
-  /// Returns whether this call is the one that decided the outcome.
   bool recordCompletion(CompletionState state)
   {
     bool recorded = false;