chore(deps): update dependency diffengine to 15.9.1 (#365)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

src/Punchclock.Tests/Punchclock.Tests.csproj

@@ -17,7 +17,7 @@
 		<PackageReference Include="Xunit.SkippableFact" Version="1.5.23" />
 		<PackageReference Include="Xunit.StaFact" Version="1.1.11" />
 		<PackageReference Include="FluentAssertions" Version="6.12.2" />
-		<PackageReference Include="DiffEngine" Version="15.5.5" />
+		<PackageReference Include="DiffEngine" Version="15.9.1" />
 		<PackageReference Include="coverlet.msbuild" Version="6.0.2">
 			<PrivateAssets>all</PrivateAssets>
 			<IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>