add link to spec issue

Author: breedx-splk

disk-buffering/src/main/java/io/opentelemetry/contrib/disk/buffering/internal/serialization/mapping/common/AttributesMapper.java

@@ -90,6 +90,8 @@ private static void addValue(AttributesBuilder builder, String key, AnyValue val
       // empty objects, we MUST assume here that the writer put an empty string
       // into the value of the attribute. This will need to change later, when complex
       // types arrive and the spec issue is resolved.
+      //
+      // See spec issue: https://github.com/open-telemetry/opentelemetry-specification/issues/4660
       builder.put(AttributeKey.stringKey(key), "");
     }
   }