[Cashtab][Alias] Open the pending aliases dropdown by default

Summary: As per UAT feedback in T3363, this diff opens the pending aliases dropdown by default.

Test Plan: Navigate to Alias.js, observe the pending aliases dropdown is open.

Reviewers: bytesofman, #bitcoin_abc, Fabien

Reviewed By: bytesofman, #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14887