Remove unused reference (#78286)

This is no longer used, which is fantastic! Less EA to worry about,
fewer dual insertions, the whole 9 meters. However, it turns out it
still happily restores and gets packaged in the LanguageServer for VS
Code. Now that razor is on 10.x the 9.x version load will cause an
exception when loading. It will eventually find the right version
because it's packaged next to the source generator in the rzls package,
but the exception is both alarming to users and slows things down. Let's
fix that.

Fixes dotnet/vscode-csharp#8193

Author: Andrew Hall

eng/Directory.Packages.props

@@ -145,7 +145,6 @@
     <PackageVersion Include="NuGet.ProjectModel" Version="6.8.0-rc.112" />
     <PackageVersion Include="Microsoft.TestPlatform.TranslationLayer" Version="$(MicrosoftNETTestSdkVersion)" />
     <PackageVersion Include="Microsoft.TestPlatform.ObjectModel" Version="$(MicrosoftNETTestSdkVersion)" />
-    <PackageVersion Include="Microsoft.AspNetCore.Razor.ExternalAccess.RoslynWorkspace" Version="9.0.0-preview.25064.4" />
 
     <!--
       Analyzers

src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Microsoft.CodeAnalysis.LanguageServer.csproj

@@ -132,7 +132,6 @@
     <PackageReference Include="Microsoft.TestPlatform.TranslationLayer" />
     <PackageReference Include="Microsoft.TestPlatform.ObjectModel" />
     <PackageReference Include="Microsoft.VisualStudio.Composition" />
-    <PackageReference Include="Microsoft.AspNetCore.Razor.ExternalAccess.RoslynWorkspace" />
     <PackageReference Include="NuGet.ProjectModel" />
     <PackageReference Include="System.CommandLine" />