build(deps): bump DiffEngine from 7.1.0 to 7.2.1 in /src (#2920)

Bumps [DiffEngine](https://github.com/VerifyTests/DiffEngine) from 7.1.0 to 7.2.1.
- [Release notes](https://github.com/VerifyTests/DiffEngine/releases)
- [Commits](https://github.com/VerifyTests/DiffEngine/commits)

---
updated-dependencies:
- dependency-name: DiffEngine
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

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

src/Directory.build.props

@@ -42,7 +42,7 @@
     <PackageReference Include="FluentAssertions" Version="6.1.0" />
     <PackageReference Include="Microsoft.Reactive.Testing" Version="5.0.0" />
     <PackageReference Include="PublicApiGenerator" Version="10.2.0" />
-    <PackageReference Include="DiffEngine" Version="7.1.0" />
+    <PackageReference Include="DiffEngine" Version="7.2.1" />
     <PackageReference Include="coverlet.msbuild" Version="3.1.0" PrivateAssets="All" />
   </ItemGroup>