Update the example project to target .NET 8

Author: tgharold

examples/OptionsPatternMvc.Example/OptionsPatternMvc.Example.csproj

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