:arrow_up: 升级xstream版本到1.4.21

pom.xml

@@ -193,7 +193,7 @@
       <dependency>
         <groupId>com.thoughtworks.xstream</groupId>
         <artifactId>xstream</artifactId>
-        <version>1.4.20</version>
+        <version>1.4.21</version>
       </dependency>
       <dependency>
         <groupId>com.google.guava</groupId>