Table cells look too large after applying and then removing paragraph formatting (e.g. heading, preformatted).

Steps to reproduce:

1. Insert → Table
2. Type text in one of the cells
   
3. Select the text and change it into a heading
   
4. Change it back into a paragraph
   

Expected: Same rendering as after step 2
Actual: The table cell is larger, and there's no way to make it smaller again (although the effect goes away after saving)