Since the introduction of the new dropzone design at [1], the dropzones were not transparent enough anymore and the inline content behind them was not readable. This commit adapts the layout of dropzones to make the content behind them more readable. [1]: https://github.com/odoo/odoo/commit/8ca644252e2d3a1f836735454c1f936529a7914e task-3537616 Part-of: odoo/odoo#137569 Co-authored-by: qsm-odoo <qsm@odoo.com>