Set property in validation csproj (#28567)

Author: safern

pkg/Microsoft.Windows.Compatibility/tests/Microsoft.Windows.Compatibility.Validation.csproj

@@ -1,6 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <PreserveCompilationContext>true</PreserveCompilationContext>
+    <!-- Setting NETCoreAppMaximumVersion to a high version so that the sdk doesn't complain if we're restoring/publishing for a higher version than the sdk. -->
+    <NETCoreAppMaximumVersion>99.9</NETCoreAppMaximumVersion>
     <PackageConflictPreferredPackages Condition="'$(TargetFramework)' != 'netcoreapp2.0'">Microsoft.Private.CoreFx.NETCoreApp;runtime.$(RID).Microsoft.Private.CoreFx.NETCoreApp;$(PackageConflictPreferredPackages)</PackageConflictPreferredPackages>
     <DisableImplicitFrameworkReferences Condition="$(TargetFramework.Contains('netcoreapp'))">true</DisableImplicitFrameworkReferences>
   </PropertyGroup>