Merge #10177: Changed "Send" button default status from true to false

Summary:
8c3e6c6 Changed "Send" button default status from true to false (KibbledJiveElkZoo)

Tree-SHA512: e60d7481351e88925d99b33bdb616f3c234e93ef052571b9c4a1328186ec9abb8b61b0c4299afcb731edad2634aef6b1adaad121646b6c0c56dc933662904674

Backport of Core PR10177

https://github.com/bitcoin/bitcoin/pull/10177/files

Test Plan:

make check
bitcoin-qt # verify that the send tx dialog defaults to Cancel rather than Yes (should be highlighted)

Reviewers: #bitcoin_abc, deadalnix, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D3282