Remove Playground branding from site list (#1700)

## Motivation for the change, related issues

We are removing because branding is not finalized yet. Mentioned by
@sfougnier
[here](#1655 (comment)).

## Implementation details

This PR hides the logo and background graphic from the site manager
sidebar.

## Testing Instructions (or ideally a Blueprint)

Run `npm run dev`, open the site listing, and observe the UI remains
visible and functional.

packages/playground/website/src/components/site-manager/site-manager-sidebar/index.tsx

@@ -11,7 +11,7 @@ import {
  __experimentalItemGroup as ItemGroup,
  __experimentalItem as Item,
 } from '@wordpress/components';
-import { Logo, TemporaryStorageIcon, WordPressIcon } from '../icons';
+import { TemporaryStorageIcon, WordPressIcon } from '../icons';
 import store, {
  PlaygroundReduxState,
  addSite as addSiteToStore,
@@ -71,7 +71,8 @@ export function SiteManagerSidebar({
  className={classNames(css.siteManagerSidebar, className)}
  >
  <header className={css.siteManagerSidebarHeader}>
- <Logo className={css.siteManagerSidebarLogoButton} />
+ {/* Remove Playground logo because branding isn't finalized. */}
+ {/* <Logo className={css.siteManagerSidebarLogoButton} /> */}
  </header>
  <nav
  className={classNames(

packages/playground/website/src/components/site-manager/style.module.css

@@ -10,7 +10,8 @@ body {
  overflow: hidden;
  padding: var(--site-manager-border-width);
  background-color: var(--site-manager-background-color);
- background-image: url(../../../public/site-manager-background.svg);
+ /* Remove Playground background graphic because branding isn't finalized. */
+ /* background-image: url(../../../public/site-manager-background.svg); */
  background-position: bottom left;
  background-repeat: no-repeat;
  width: 100%;