[e.cash] Force live tx text to bottom of card

Summary:
If there are not 4 tx present the "live transactions" text is not pinned to the bottom of the card. This css rule fixes that

Test Plan: preview and check

Reviewers: #bitcoin_abc, Kronkmeister

Reviewed By: #bitcoin_abc, Kronkmeister

Subscribers: Fabien, Kronkmeister

Differential Revision: https://reviews.bitcoinabc.org/D19415