Un-deprecate webviewPanel.viewColumn

This property was deprecated initially as we were not sure how grid layout would work. Since it is using viewColumns, we are un-deprecating this

src/vs/vscode.d.ts

@@ -5513,8 +5513,6 @@ declare module 'vscode' {
 		/**
 		 * Editor position of the panel. This property is only set if the webview is in
 		 * one of the editor view columns.
-		 *
-		 * @deprecated
 		 */
 		readonly viewColumn?: ViewColumn;