Update README_CN.md (#762)

修改版本号,2.7.7->2.7.8
diff --git a/README_CN.md b/README_CN.md
index 4db54ce..e1e42cc 100644
--- a/README_CN.md
+++ b/README_CN.md
@@ -22,7 +22,7 @@
 ```xml
 <properties>
     <spring-boot.version>2.3.0.RELEASE</spring-boot.version>
-    <dubbo.version>2.7.7</dubbo.version>
+    <dubbo.version>2.7.8</dubbo.version>
 </properties>
     
 <dependencyManagement>
@@ -72,7 +72,7 @@
     <dependency>
         <groupId>org.apache.dubbo</groupId>
         <artifactId>dubbo-spring-boot-starter</artifactId>
-        <version>2.7.7</version>
+        <version>2.7.8</version>
     </dependency>
     
     <dependency>