Update Directory.Build.props

Author: michael-hawker

Directory.Build.props

@@ -4,7 +4,7 @@
     <Authors>Microsoft.Toolkit</Authors>
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>
     <NoPackageAnalysis>true</NoPackageAnalysis>
-    <PackageIconUrl>https://raw.githubusercontent.com/windows-toolkit/WindowsCommunityToolkit/master/build/nuget.png</PackageIconUrl>
+    <PackageIconUrl>https://raw.githubusercontent.com/windows-toolkit/WindowsCommunityToolkit/main/build/nuget.png</PackageIconUrl>
     <PackageIcon>images\nuget.png</PackageIcon>
     <PackageProjectUrl>https://github.com/windows-toolkit/WindowsCommunityToolkit</PackageProjectUrl>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>    
@@ -109,4 +109,4 @@
 
   <Import Project="$(MSBuildThisFileDirectory)build\Windows.Toolkit.VisualStudio.Design.props" Condition="'$(IsDesignProject)' == 'true'"/>
 
-</Project>
+</Project>