Fix idle in druid instrumentation (#11079)

Author: AlchemyDing

instrumentation/alibaba-druid-1.0/library/src/main/java/io/opentelemetry/instrumentation/alibabadruid/v1_0/ConnectionPoolMetrics.java

@@ -40,9 +40,7 @@ public static void registerMetrics(
         metrics.batchCallback(
             () -> {
               connections.record(dataSource.getActiveCount(), usedConnectionsAttributes);
-              connections.record(
-                  dataSource.getPoolingCount() - dataSource.getActiveCount(),
-                  idleConnectionsAttributes);
+              connections.record(dataSource.getPoolingCount(), idleConnectionsAttributes);
               pendingRequestsForConnection.record(dataSource.getWaitThreadCount(), attributes);
               minIdleConnections.record(dataSource.getMinIdle(), attributes);
               maxIdleConnections.record(dataSource.getMaxIdle(), attributes);