Upgrade target framework from net462 to net8.0

Author: torosent

samples/DurableTask.Samples/DurableTask.Samples.csproj

@@ -4,7 +4,7 @@
   <PropertyGroup>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net462</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>