Bump MarkdownSnippets.MsBuild from 28.0.0-beta.2 to 28.0.0-beta.8

---
updated-dependencies:
- dependency-name: MarkdownSnippets.MsBuild
  dependency-version: 28.0.0-beta.8
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

src/Directory.Packages.props

@@ -5,7 +5,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageVersion Include="DocumentFormat.OpenXml" Version="3.3.0" />
-    <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.0.0-beta.2" />
+    <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.0.0-beta.8" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
     <PackageVersion Include="NUnit" Version="4.4.0" />
     <PackageVersion Include="NUnit3TestAdapter" Version="5.1.0" />