[FIX] web_editor: remove redundant code from setTagName

Commit [1] implemented an approach for changing style of a list item to normal.
It no longer wrapped the content in a <p> to remove extra spacing to next list
item. Later commit [2] was introduced which did the same thing but in sanatize.
Hence the code added in commit [1] is no longer needed.
This commit removes the redundant code from `setTagName`.

[1]: 03a134c7
[2]: 324e1387

closes odoo/odoo#141812

X-original-commit: bd1e432d
Signed-off-by: Antoine Guenet (age) <age@odoo.com>