[Cashtab] Remove dirty param from SendToken formData

Summary: In SendToken, fromData included an unused 'dirty' param which has been removed. Related to task T2108

Test Plan:
cd web/cashtab && npm start
navigate to the tokens tab, then the send token page
send token and ensure transaction is successful

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D10767