chore: bump the trimming project version

Author: Andrew Omondi

tests/Microsoft.Graph.DotnetCore.Core.Trimming/Microsoft.Graph.DotnetCore.Core.Trimming.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
         <OutputType>Exe</OutputType>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net9.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <InvariantGlobalization>true</InvariantGlobalization>