Removed trailing whitespace in .csproj

Author: Sergio0694

Microsoft.Toolkit.Mvvm/Microsoft.Toolkit.Mvvm.csproj

@@ -22,7 +22,7 @@
     <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="1.1.1" />
     <PackageReference Include="System.Memory" Version="4.5.4" />
   </ItemGroup>
-  
+
   <!-- .NET Standard 2.1 doesn't have the Unsafe type -->
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.1' ">
     <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="4.7.1" />