build(deps): bump DiffEngine from 6.4.8 to 6.4.9 in /src (#2624)

Bumps [DiffEngine](https://github.com/VerifyTests/DiffEngine) from 6.4.8 to 6.4.9.
- [Release notes](https://github.com/VerifyTests/DiffEngine/releases)
- [Commits](https://github.com/VerifyTests/DiffEngine/commits)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

src/Directory.build.props

@@ -50,7 +50,7 @@
     <PackageReference Include="FluentAssertions" Version="5.10.3" />
     <PackageReference Include="Microsoft.Reactive.Testing" Version="5.0.0" />
     <PackageReference Include="PublicApiGenerator" Version="10.2.0" />
-    <PackageReference Include="DiffEngine" Version="6.4.8" />
+    <PackageReference Include="DiffEngine" Version="6.4.9" />
     <PackageReference Include="coverlet.msbuild" Version="2.9.0" PrivateAssets="All" />
   </ItemGroup>