Fix after merge

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Formatting/DocumentOnTypeFormattingEndpoint.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Frozen;
 using System.Collections.Immutable;
 using System.Diagnostics;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Language;