change unit to '1'

Author: SylvainJuge

instrumentation/jmx-metrics/library/src/main/java/io/opentelemetry/instrumentation/jmx/yaml/JmxRule.java

@@ -207,7 +207,7 @@ private static List<MetricExtractor> createStateMappingExtractors(
               metricInfo.getMetricName(),
               metricInfo.getDescription(),
               null,
-              "",
+              "1",
               MetricInfo.Type.UPDOWNCOUNTER);
 
       extractors.add(new MetricExtractor(extractor, stateMetricInfo, stateMetricAttributes));