Fix "QuickStart => TourInfo" empty space when no info present

Created by: erzhtor

Closes https://github.com/sourcegraph/sourcegraph/issues/36111.

Screenshots

BEFORE	AFTER

Test plan

• SOURCEGRAPH_API_URL=https://sourcegraph.com SOURCEGRAPHDOTCOM_MODE=true sg start web-standalone
• Force show quick start tour
  • Go to https://sourcegraph.test:3443/search and sign out (if signed in)
  • Clear quick-start-tour local storage item (if already it previously closed)
• Search or go to any file page and make sure no empty gap is rendered on top
• Click quick start tour item and make sure info panel (green box with text) renders as previsously

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.