Remove net5.0 of core project, wasn't really needed

global.json

@@ -1,6 +0,0 @@
-{
-    "sdk": {
-        "version": "5.0.101",
-        "rollForward": "feature"
-    }
-}

src/Microsoft.Maui.Graphics/Microsoft.Maui.Graphics.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="MSBuild.Sdk.Extras">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.1;netstandard2.0;net5.0;Xamarin.iOS10;MonoAndroid10.0;Xamarin.Mac20;</TargetFrameworks>
+    <TargetFrameworks>netstandard2.1;netstandard2.0;Xamarin.iOS10;MonoAndroid10.0;Xamarin.Mac20;</TargetFrameworks>
       <!-- Optional: Publish the repository URL in the built .nupkg (in the NuSpec <Repository> element) -->
       <PublishRepositoryUrl>true</PublishRepositoryUrl>
       <!-- Optional: Build symbol package (.snupkg) to distribute the PDB containing Source Link -->