Remove gap between tree scroll bar and visualiser resize handle

Summary:
So much tidier

changelog: UIDebugger remove gap between tree and visualiser

Reviewed By: lblasa

Differential Revision: D43307743

fbshipit-source-id: ceec9b3b164c93ecadfe8c0b7299a978b2915e3b

desktop/plugins/public/ui-debugger/components/main.tsx

@@ -50,8 +50,8 @@ export function Component() {
         <Layout.Container grow padh="small" padv="medium">
           {instance.device === 'iOS' ? <FeedbackRequest /> : null}
           <Controls />
-          <Layout.Horizontal grow pad="small" gap="small">
-            <Layout.Container grow gap="small">
+          <Layout.Horizontal grow pad="small">
+            <Layout.Container grow>
               <Layout.ScrollContainer>
                 <Tree2 nodes={nodes} rootId={rootId} />
               </Layout.ScrollContainer>