Fix build

Author: davidwengier

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Endpoints/RazorCustomMessageTarget_CodeActions.cs

@@ -10,7 +10,6 @@
 using Microsoft.CodeAnalysis.Razor.Protocol.CodeActions;
 using Microsoft.CodeAnalysis.Razor.Telemetry;
 using Microsoft.VisualStudio.LanguageServer.ContainedLanguage;
-using Microsoft.VisualStudio.Threading;
 using StreamJsonRpc;
 
 namespace Microsoft.VisualStudio.Razor.LanguageClient.Endpoints;