Dropdown - Disable applyStyle modifier instead of removing inline style + Popper.js update

Created by: Johann-S

In #22782 we chose to remove the inline style by adding a modifier because they were an issue in Popper.js (see: https://github.com/FezVrasta/popper.js/issues/309) but this issue has been fixed so now we can simply disable applyStyle modifier.

Thank you @FezVrasta 👍

I added a unit test for code consistency and updated Popper.js