In Odoo v16, you can remove the checkboxes from the tree view in a wizard by setting the "selectable" attribute to "none" in the view's xml definition.

Here is an example:

...

You can also remove the checkboxes from the tree view by setting the "selectable" attribute to "none" directly in the action definition, like this:

In both cases, setting the "selectable" attribute to "none" will remove the checkboxes from the tree view and prevent users from selecting multiple records.