Revert "(#86) Embed README in the NuGet package"

Adding the README to the package is currently blocked by
NuGet/Home#10791

This reverts commit 2cacf5e.

src/Ookii.Dialogs.Wpf/Ookii.Dialogs.Wpf.csproj

@@ -41,7 +41,6 @@
     <Copyright>Copyright (c) 2009-2021 Ookii Dialogs Contributors</Copyright>
     <PackageTags>ookii;dialogs;wpf;windows-presentation-foundation;progress-dialog;task-dialog;credential-dialog;common-file-dialog</PackageTags>
     <PackageLicenseExpression>BSD-3-Clause</PackageLicenseExpression>
-    <PackageReadmeFile>README.md</PackageReadmeFile>
     <PackageIcon>images\icon.png</PackageIcon>
     <PackageIconUrl>https://raw.githubusercontent.com/ookii-dialogs/ookii-dialogs-wpf/master/assets/ookii-dialogs-wpf-nuget.png</PackageIconUrl>
     <PackageProjectUrl>https://github.com/ookii-dialogs/ookii-dialogs-wpf</PackageProjectUrl>
@@ -147,7 +146,6 @@
   </ItemGroup>
 
   <ItemGroup>
-    <None Include="..\..\README.md" Pack="true" Visible="false" PackagePath="README.md" />
     <None Include="..\..\assets\ookii-dialogs-wpf-nuget.png" Pack="true" Visible="false" PackagePath="images\icon.png" />
   </ItemGroup>