[Cashtab] Add correct dev dependency for ESlint types in jest

Summary:
Prelim for T2088

Cashtab devs will see linting errors in their IDE for all test files as the correct dev dependency for the jest types used is not installed. This diff corrects the issue.

Test Plan:

1. Open any .test.js file in VS code
2. Confirm jest terms are not highlighted in red as lint errors (e.g. it, describe, expect)

Reviewers: Fabien, emack, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D10770