Revert + adjust "Ensure slash in PublishDir" (dotnet#11401)

### Context
dotnet#11248 broke ClickOnce publishing -
https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2359773
The breakage is caused by the 'NormalizePath' part - as it can change
relative path to absolute.

### Changes made
- reverted
- added the original change, which just ensures the slash

src/Tasks/Microsoft.Common.CurrentVersion.targets

@@ -497,7 +497,7 @@ Copyright (C) Microsoft Corporation. All rights reserved.
   <!-- Output location for publish target. -->
   <PropertyGroup>
     <PublishDir Condition="'$(PublishDir)' != '' and !HasTrailingSlash('$(PublishDir)')">$(PublishDir)\</PublishDir>
-    <PublishDir Condition="'$(PublishDir)'==''">$([MSBuild]::EnsureTrailingSlash($([MSBuild]::NormalizePath('$(OutputPath)', 'app.publish'))))</PublishDir>
+    <PublishDir Condition="'$(PublishDir)'==''">$([MSBuild]::EnsureTrailingSlash('$(OutputPath)'))app.publish\</PublishDir>
   </PropertyGroup>
 
   <!--