downgrade package version.

fix compile error on mac.

Author: sang-hyeon

src/PlasticCommand/PlasticCommand.csproj

@@ -47,7 +47,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.7.0" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.6.0" PrivateAssets="all" />
     <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" PrivateAssets="all" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="7.0.0" />