Update Directory.Packages.props

Author: SimonCropp

src/Directory.Packages.props

@@ -5,9 +5,9 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.0.0-beta.8" />
-    <PackageVersion Include="Microsoft.CodeAnalysis.Analyzers" Version="3.11.0" />
-    <PackageVersion Include="Microsoft.CodeAnalysis.CSharp" Version="4.9.2" />
-    <PackageVersion Include="Microsoft.CodeAnalysis.VisualBasic" Version="4.9.2" />
+    <PackageVersion Include="Microsoft.CodeAnalysis.Analyzers" Version="3.11.0" Pinned="true" />
+    <PackageVersion Include="Microsoft.CodeAnalysis.CSharp" Version="4.9.2" Pinned="true" />
+    <PackageVersion Include="Microsoft.CodeAnalysis.VisualBasic" Version="4.9.2" Pinned="true" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
     <PackageVersion Include="Polyfill" Version="9.3.1" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.163" />