#7643119 Update/videopress onboarding celebration modal

Proposed Changes

• copy and style changes for the Video celebration modal used by VideoPress onboarding

before	after

Testing Instructions

1. run install-plugin.sh editing-toolkit update/videopress-onboarding-celebration-modal on your wpcom sandbox
2. go through the onboarding flow to the point where you upload your first video and save the page
   • NOTE: If you want to test with an existing site instead of setting up a new one, you can set wp-content/plugins/editing-toolkit-plugin/prod/wpcom-block-editor-nux/class-wp-rest-wpcom-block-editor-video-celebration-modal-controller.php on your sandbox to return false on line 86.
3. you should see the new celebration modal
4. Launch the Welcome Guide, and confirm that the video specific images are still displayed

Pre-merge Checklist

• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the “[Status] String Freeze” label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the “[Status] Needs Privacy Updates” label if this pull request changes what data or activity we track or use (p4TIVU-ajp-p2)?

Related to # Automattic/greenhouse#1392