Avoid upgrading the packages for ICSharpCode.Decompiler.csproj

Author: cshung

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -84,8 +84,8 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="System.Collections.Immutable" Version="10.0.0-preview.3.25171.5" />
-    <PackageReference Include="System.Reflection.Metadata" Version="10.0.0-preview.3.25171.5" />
+    <PackageReference Include="System.Collections.Immutable" Version="6.0.0" />
+    <PackageReference Include="System.Reflection.Metadata" Version="6.0.0" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>