Align images to the right by using an auto left margin.

Steps to reproduce:
- Drop a "Columns" block.
- Select an image.
- Resize image to 50%.
- Align image to the right.
=> Image did not get aligned to the right.

task-2841127

X-original-commit: 785ea10014c9ab3bd8da9eeecd2d6910786edbc7
Part-of: odoo/odoo#118657