[Cashtab] Do not change text color on hover for link button

Summary: Hangover from antd deprecation. PrimaryButton as link will catch <a> styles. Block the ones we do not want. More specific title for the button so it does not tooltip the parent component.

Test Plan:
npm test, review screenshots

Before this diff:

After this diff:

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D15950