Transactions - make "show older" area bigger and include keyboard command

Summary: Fixes T6683.

Test Plan: clicked the yellow box and it worked! pressed '~' and it worked!

Reviewers: epriestley, chad

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6683

Differential Revision: https://secure.phabricator.com/D10932