[Cashtab] Update airdrop.js with direct antd calls

Summary:
Replacing Notification.js usage with direct antd API calls at callsite.

As per tg discussion, not creating integration test to retest existing functionality until we have a diff that changes the component. Using manual tests for now.

Test Plan:

• Navigate to Airdrop
• Calculate an airdrop with Minimum eToken holder balance set to a large number
• Ensure error notification No holders found for eToken ID: (token ID) is rendered
• Create a new token
• Attempt to calculate an airdrop for the new token (with no holders) and ensure error notification.
• Malform config/token.js/tokenDbUrl and ensure error notification.

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D15468