Actually this is not a signing transaction, but rather authenticating logged in
user when he wants to send a transaction. An authentication is done by entering
password(regular user) or pin(keycard user).
A real signing transaction feature will be (hopefully) added in a near future where
we're going to sign a transaction on a keycard which corresponds to a certain
account, a user wants to send a transaction from.
To sum up... this change just removes password from the send modal and introduces
`Authenticate` flow instead.
Fixes: #7510