Prepare for release 5.2.0 (#839)

Co-authored-by: tsaitsung-han.tht <tsaitsung-han.tht@alibaba-inc.com>

Author: tsunghanjacktsai

csharp/rocketmq-client-csharp/rocketmq-client-csharp.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
         <PackageId>RocketMQ.Client</PackageId>
-        <PackageVersion>5.1.1-rc1</PackageVersion>
+        <PackageVersion>5.2.0-rc1</PackageVersion>
         <Version>$(PackageVersion)</Version>
 
         <Authors>RocketMQ Authors</Authors>