Fix NewtonSoft reference path.

Remove unused ProBuildCore reference.

SongBrowserPlugin/SongBrowser.csproj

@@ -53,15 +53,12 @@
     <Reference Include="MainAssembly">
       <HintPath>D:\Games\Steam\SteamApps\common\Beat Saber\Beat Saber_Data\Managed\MainAssembly.dll</HintPath>
     </Reference>
-    <Reference Include="Newtonsoft.Json">
-      <HintPath>C:\Program Files (x86)\Steam\steamapps\common\Beat Saber\Beat Saber_Data\Managed\Newtonsoft.Json.dll</HintPath>
+    <Reference Include="Newtonsoft.Json.12.0.0.0">
+      <HintPath>D:\Games\Steam\SteamApps\common\Beat Saber\Libs\Newtonsoft.Json.12.0.0.0.dll</HintPath>
     </Reference>
     <Reference Include="Polyglot.Scripts">
       <HintPath>C:\Program Files (x86)\Steam\steamapps\common\Beat Saber\Beat Saber_Data\Managed\Polyglot.Scripts.dll</HintPath>
     </Reference>
-    <Reference Include="ProBuilderCore">
-      <HintPath>C:\Program Files (x86)\Steam\steamapps\common\Beat Saber\Beat Saber_Data\Managed\ProBuilderCore.dll</HintPath>
-    </Reference>
     <Reference Include="SongCore">
       <HintPath>D:\Games\Steam\SteamApps\common\Beat Saber\Plugins\SongCore.dll</HintPath>
     </Reference>