[FIX] web_editor: same style on div and p in backend in edit mode

Before this commit:
In the web_editor in backend, entering edit mode would display differently text
in `div` and text in `p` but not when viewing the content outside edit mode.

Now, `div` and `p` won't have different style when entering edit mode.

addons/web_editor/static/src/less/web_editor.backend.less

@@ -5,7 +5,7 @@
         font-family: inherit !important;
         line-height: initial !important;
         color: initial !important;
-        p {
+        p, div {
             font-family: 'Lucida Grande', Helvetica, Verdana, Arial, sans-serif;
             font-size: 13px;
         }