US-1889327: Updated column headers. (#1329)

* Column header fixes for US-1889327.

* Metadata update.

dotnet-desktop-guide/xaml-services/xuid-directive.md

@@ -1,6 +1,8 @@
 ---
 title: "x:Uid Directive"
+description: Learn about the x:Uid Directive.
 ms.date: "03/30/2017"
+ms.custom: devdivchpfy22
 helpviewer_keywords: 
   - "XAML [XAML Services], localizable content attribute"
   - "XAML [XAML Services], x:Uid attribute"
@@ -20,8 +22,8 @@ Provides a unique identifier for markup elements. In many scenarios, this unique
 
 ## XAML Values
 
-|||
-|-|-|
+| Value | Description |
+|-------|-------------|
 |`identifier`|A manually created or autogenerated string that should be unique in a file when it is interpreted by an `x:Uid` consumer.|
 
 ## Remarks