Fix ApiCompatEnableRuleCannotChangeParameterName prop (#28344)

This should be an msbuild property, not an item.

Author: ViktorHofer

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.ApiCompat.ValidatePackage.targets

@@ -40,7 +40,7 @@ Copyright (c) .NET Foundation. All rights reserved.
       NoWarn="$(NoWarn)"
       EnableRuleAttributesMustMatch="$(ApiCompatEnableRuleAttributesMustMatch)"
       ExcludeAttributesFiles="@(ApiCompatExcludeAttributesFile)"
-      EnableRuleCannotChangeParameterName="@(ApiCompatEnableRuleCannotChangeParameterName)"
+      EnableRuleCannotChangeParameterName="$(ApiCompatEnableRuleCannotChangeParameterName)"
       RunApiCompat="$(RunApiCompat)"
       EnableStrictModeForCompatibleTfms="$([MSBuild]::ValueOrDefault('$(EnableStrictModeForCompatibleTfms)', 'true'))"
       EnableStrictModeForCompatibleFrameworksInPackage="$(EnableStrictModeForCompatibleFrameworksInPackage)"