Update DiscordRichPresence package reference to 1.0.147 which is now built for .NET core (#898)

Ryujinx/Ryujinx.csproj

@@ -70,7 +70,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="DiscordRichPresence" Version="1.0.121" />
+    <PackageReference Include="DiscordRichPresence" Version="1.0.147" />
     <PackageReference Include="GtkSharp" Version="3.22.25.24" />
     <PackageReference Include="GtkSharp.Dependencies" Version="1.1.0" Condition="'$(RuntimeIdentifier)' != 'linux-x64' AND '$(RuntimeIdentifier)' != 'osx-x64'" />
     <PackageReference Include="OpenTK.NetStandard" Version="1.0.4" />