Fix a typo in french (fr) translation

Summary:
In the send coin dialog GUI, the "Send" button should translate to
"Envoyer" instead of "Evoyer". This is only present in the fr_FR
variant.

Test Plan:

Open the GUI send coin dialog with the language settings set to fr_FR

and check the translation is correct.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2334