[Cashtab] Do not clearTimeout when alias component unmounts

Summary:
Since this is a timeout, and not an interval, we are only clearing one possible extra call.

In testing, this clearance is not working. So, stop trying to do this.

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D15337