In RTL editor indent performs outdent and vise versa

[mark-k]

1. In hebrew localization start editing a post
2. start a unordered list
3. add an item to the list
4. try to outdent it (the first button of the indent/outdent pair from the right as expected)
5. the item was indented

the action performed is not consistent with the icon, but it is consistent with the tooltip text.

Duplicate of #21281.