[release/7.0-rc1] Make Microsoft.AspNetCore.Grpc.Swagger experimental (#43384)

Author: JamesNK

src/Grpc/JsonTranscoding/src/Microsoft.AspNetCore.Grpc.Swagger/Microsoft.AspNetCore.Grpc.Swagger.csproj

@@ -3,8 +3,7 @@
     <Description>Swagger for gRPC ASP.NET Core</Description>
     <PackageTags>gRPC RPC HTTP/2 REST Swagger OpenAPI</PackageTags>
     <TargetFramework>$(DefaultNetCoreTargetFramework)</TargetFramework>
-    <IsPackable>false</IsPackable>
-    <IsShipping>false</IsShipping>
+    <VersionPrefix>$(ExperimentalVersionPrefix)</VersionPrefix>
   </PropertyGroup>
 
   <ItemGroup>