Bump netty-all version in sentinel-demo-dubbo to fix vulnerability (#1130)

Bumps [netty-all](https://github.com/netty/netty) from 4.1.31.Final to 4.1.42.Final.

Signed-off-by: dependabot[bot] <support@github.com>

sentinel-demo/sentinel-demo-dubbo/pom.xml

@@ -25,7 +25,7 @@
         <dependency>
             <groupId>io.netty</groupId>
             <artifactId>netty-all</artifactId>
-            <version>4.1.31.Final</version>
+            <version>4.1.42.Final</version>
         </dependency>
 
         <!-- As demo use @DubboComponentScan to config, which is implemented in dubbo-config-spring module -->