refs or cleanup

Author: SimonCropp

src/Directory.Build.props

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <Version>6.2.1</Version>
     <LangVersion>preview</LangVersion>
+    <NoWarn>NU1608</NoWarn>
     <AssemblyVersion>1.0.0</AssemblyVersion>
     <PackageTags>Clipboard, Copy</PackageTags>
     <Description>A cross platform package to copy text to the clipboard.</Description>

src/Directory.Packages.props

@@ -13,7 +13,7 @@
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.13.0" />
     <PackageVersion Include="Microsoft.NETCore.UniversalWindowsPlatform" Version="6.2.13" />
     <PackageVersion Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.3" />
-    <PackageVersion Include="Polyfill" Version="7.24.0" />
+    <PackageVersion Include="Polyfill" Version="7.26.0" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.144" />
     <PackageVersion Include="PropertyChanged.Fody" Version="4.1.0" />
     <PackageVersion Include="System.Runtime.InteropServices.RuntimeInformation" Version="4.3.0" />