remove unused imports (EnableDubboLifecycle) (#344)

diff --git a/dubbo-samples-sentinel/src/main/java/org/apache/samples/sentinel/provider/ProviderConfiguration.java b/dubbo-samples-sentinel/src/main/java/org/apache/samples/sentinel/provider/ProviderConfiguration.java
index 6c87897..553c88a 100644
--- a/dubbo-samples-sentinel/src/main/java/org/apache/samples/sentinel/provider/ProviderConfiguration.java
+++ b/dubbo-samples-sentinel/src/main/java/org/apache/samples/sentinel/provider/ProviderConfiguration.java
@@ -20,9 +20,7 @@
 import org.apache.dubbo.config.ApplicationConfig;
 import org.apache.dubbo.config.ProtocolConfig;
 import org.apache.dubbo.config.RegistryConfig;
-import org.apache.dubbo.config.spring.context.annotation.DubboComponentScan;
 import org.apache.dubbo.config.spring.context.annotation.EnableDubbo;
-import org.apache.dubbo.config.spring.context.annotation.EnableDubboLifecycle;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Bean;