Change sendcoins dialogue Yes to Send (Gregory Sanders)
Pull request description:
It's more self-explanatory, matches "cancel" better, and makes future extensions such as https://github.com/bitcoin/bitcoin/pull/16944 more directly understandable to the user.
https://github.com/bitcoin/bitcoin/pull/16964/commits/a649cc6a17b8d8d602c6b67037b0c926960f9cdb
Backport of Core PR16964