build(deps): bump DiffEngine from 6.7.0 to 6.8.0 in /src (#674)

Bumps [DiffEngine](https://github.com/VerifyTests/DiffEngine) from 6.7.0 to 6.8.0.
- [Release notes](https://github.com/VerifyTests/DiffEngine/releases)
- [Commits](https://github.com/VerifyTests/DiffEngine/commits/6.8.0)

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

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

src/Akavache.Tests/Akavache.Tests.csproj

@@ -21,7 +21,7 @@
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
     <PackageReference Include="SQLitePCLRaw.bundle_e_sqlite3" Version="2.0.4" />
     <PackageReference Include="FluentAssertions" Version="5.10.3" />
-    <PackageReference Include="DiffEngine" Version="6.7.0" />
+    <PackageReference Include="DiffEngine" Version="6.8.0" />
     <PackageReference Include="PublicApiGenerator" Version="10.2.0" />
     <PackageReference Include="coverlet.msbuild" Version="3.0.3">
       <PrivateAssets>all</PrivateAssets>