fixed clippy issues

Author: kumarUjjawal

tests-integration/src/cluster.rs

@@ -441,7 +441,6 @@ impl GreptimeDbClusterBuilder {
             instance,
             servers,
             heartbeat_task: Some(heartbeat_task),
-            export_metrics_task: None,
         }
     }
 

tests-integration/src/standalone.rs

@@ -288,7 +288,6 @@ impl GreptimeDbStandaloneBuilder {
             instance,
             servers: ServerHandlers::default(),
             heartbeat_task: None,
-            export_metrics_task: None,
         };
 
         frontend.start().await.unwrap();