[e.cash] Fix subpage hero display issue

Summary:
There were some display issues with the hero section height/video background height. fixing with some CSS tweaks

Basic issue before was the video background and the hero container height were disjointed resulting in some weird alignment on extra tall screen, and a shortened video background on small screens

Test Plan:
npm run dev or preview site
navigate to /wealth-redefined page
inspect the hero section on an extra tall screen. You can use developer tools and set the screen height to like 1500
it should look okay here, ie text and image is lined up and hero section video background doesnt have weird gaps.

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D14061