Delete ImportDocumentSnapshot now that it is unused

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/ImportDocumentSnapshot.cs

@@ -1,72 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the MIT license. See License.txt in the project root for license information.
-
-using System;
-using System.Diagnostics.CodeAnalysis;
-using System.Threading;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Razor;
-using Microsoft.AspNetCore.Razor.Language;
-using Microsoft.CodeAnalysis.Text;
-
-namespace Microsoft.CodeAnalysis.Razor.ProjectSystem;
-
-internal sealed class ImportDocumentSnapshot(IProjectSnapshot project, RazorProjectItem item) : IDocumentSnapshot
-{
-    public IProjectSnapshot Project { get; } = project;
-
-    private readonly RazorProjectItem _importItem = item;
-    private SourceText? _text;
-
-    // The default import file does not have a kind or paths.
-    public string? FileKind => null;
-    public string? FilePath => null;
-    public string? TargetPath => null;
-
-    public int Version => 1;
-
-    public ValueTask<SourceText> GetTextAsync(CancellationToken cancellationToken)
-    {
-        return TryGetText(out var text)
-            ? new(text)
-            : ReadTextAsync();
-
-        ValueTask<SourceText> ReadTextAsync()
-        {
-            using var stream = _importItem.Read();
-            var sourceText = SourceText.From(stream);
-
-            var result = _text ??= InterlockedOperations.Initialize(ref _text, sourceText);
-            return new(result);
-        }
-    }
-
-    public ValueTask<RazorCodeDocument> GetGeneratedOutputAsync(
-        bool forceDesignTimeGeneratedOutput,
-        CancellationToken cancellationToken)
-        => throw new NotSupportedException();
-
-    public ValueTask<VersionStamp> GetTextVersionAsync(CancellationToken cancellationToken)
-        => new(VersionStamp.Default);
-
-    public bool TryGetText([NotNullWhen(true)] out SourceText? result)
-    {
-        result = _text;
-        return result is not null;
-    }
-
-    public bool TryGetTextVersion(out VersionStamp result)
-    {
-        result = VersionStamp.Default;
-        return true;
-    }
-
-    public bool TryGetGeneratedOutput([NotNullWhen(true)] out RazorCodeDocument? result)
-        => throw new NotSupportedException();
-
-    public IDocumentSnapshot WithText(SourceText text)
-        => throw new NotSupportedException();
-
-    public ValueTask<SyntaxTree> GetCSharpSyntaxTreeAsync(CancellationToken cancellationToken)
-        => throw new NotSupportedException();
-}