Fixed the alignment in the MR widget

## What does this MR do?

Fixes the alignment of the browse button in the MR widget

## Screenshots (if relevant)

![Screen_Shot_2016-07-17_at_17.47.54](/uploads/41dcb0fad38fdd4dbccfda5ffaeaec6e/Screen_Shot_2016-07-17_at_17.47.54.png)

See merge request !5307