fix: src/TestSite.10/TestSite.10.csproj to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DOTNET-SIXLABORSIMAGESHARP-9298862
- https://snyk.io/vuln/SNYK-DOTNET-UMBRACOCMSWEBBACKOFFICE-9399124

Author: snyk-bot

src/TestSite.10/TestSite.10.csproj

@@ -7,7 +7,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Umbraco.Cms" Version="10.8.8"/>
+        <PackageReference Include="Umbraco.Cms" Version="10.8.9"/>
         <PackageReference Include="uSync" Version="10.7.3"/>
     </ItemGroup>