Updating version to 3.1.0-preview

Author: makam

src/Microsoft.Azure.ServiceBus/Microsoft.Azure.ServiceBus.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <Description>This is the next generation Azure Service Bus .NET Standard client library that focuses on queues &amp; topics. For more information about Service Bus, see https://azure.microsoft.com/en-us/services/service-bus/</Description>
-    <Version>3.0.2</Version>
+    <Version>3.1.0-preview</Version>
     <Authors>Microsoft</Authors>
     <TargetFramework>netstandard2.0</TargetFramework>
     <AssemblyOriginatorKeyFile>../../build/keyfile.snk</AssemblyOriginatorKeyFile>