[MR Widget V2] Position the widget correctly

Summary

The MR Widget V2 is not positioned correctly with other widgets.

current	expected

Implementation plan

• Change the position of the widget and adjust it according to the expected screenshot in app/assets/javascripts/vue_merge_request_widget/mr_widget_options.vue
• Change the position of the widget and adjust it according to the expected screenshot in ee/app/assets/javascripts/vue_merge_request_widget/mr_widget_options.vue