[website] Change title on landing page copy

Summary: Changed "Get Started" into "Introdcuing eCash" and removed last sentence

Test Plan: visit e.cash and scroll down to "introducing eCash" copy.

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D16247