Improve accept mr widget UI

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Fix tests

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'improve-merge-widget' into 'master'

Improve merge widget

* remove title `You can merge it` since button below says same
* fixed layout for custom commit message
* make button a bit bigger

See merge request !1365