Updates target framework to .NET 8

Author: neoscie

Neolution.Extensions.Caching.UnitTests/Neolution.Extensions.Caching.UnitTests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <IsPackable>false</IsPackable>
     <LangVersion>latest</LangVersion>
   </PropertyGroup>