Delete vstest patch that was backported with 21bc097b12

src/SourceBuild/patches/vstest/0001-Remove-explicit-framework-ref-assembly-ref.patch

@@ -1,27 +0,0 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: Matt Mitchell <mmitche@microsoft.com>
-Date: Wed, 19 Apr 2023 09:30:15 -0700
-Subject: [PATCH] Remove explicit framework ref assembly ref The SDK brings
- this implicitly when targeting a net4* TFM
-
-Backport: https://github.com/microsoft/vstest/pull/4407
----
- Directory.Build.targets | 5 -----
- 1 file changed, 5 deletions(-)
-
-diff --git a/Directory.Build.targets b/Directory.Build.targets
-index 5077c4638..b720568ba 100644
---- a/Directory.Build.targets
-+++ b/Directory.Build.targets
-@@ -11,11 +11,6 @@
-     <TargetFramework Condition=" '$(TargetFramework)' != '' ">$(NetCurrent)</TargetFramework>
-   </PropertyGroup>
- 
--  <!-- Allows build of .NET Framework assemblies on MacOS and Linux https://github.com/dotnet/designs/pull/33#issuecomment-489264196 -->
--  <ItemGroup>
--    <PackageReference Condition=" '$(OS)' != 'Windows_NT' " Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.2" PrivateAssets="All" />
--  </ItemGroup>
--
-   <!-- Test project settings -->
-   <Choose>
-     <When Condition="$(TestProject) == 'true'">