[Cashtab] Removed unused var from Send.js.

Summary: Removed unused var 'value' from formData var in Send.js at line 252. Related to task T2104.

Test Plan:
Navigate to web/cashtab/components/Send/Send.js
Inside the isOneToManyXECSend if block, check to ensure 'value' is removed from the object on line 252.

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D10763