[FIX] website, *: allow to re-edit company team snippet images

*: web_editor

Since [1], it was not possible to edit a company team snippet image
anymore as soon as the page was saved once. Indeed that commit added
o_not_editable/contenteditable="false" on the parent column to make sure
no text can be added in that column and contenteditable="true" on the
images so that they are still editable (even though HTML-specs-wise
adding contenteditable="true" on images probably does not mean much as
images are self-closing tags, our editor understand that as the ability
to edit the image anyway). That contenteditable="true" part is however
removed when leaving edit mode... and was not restored upon entering
edit mode again.

This fixes the problems with an ugly patch. We'll review what to do in
master.

Funny enough, that bug was actually gone in 15.0... by mistake. A recent
bug fix actually reintroduced that isolated bug at [2] (by reintroducing
the fact that images in a non-editable environment are not possible to
edit). The 3 opened tickets this commit mentions were actually reported
for 15.0 immediately after that, while the 14.0 being broken about this
since the beginning apparently did not bother anyone.

[1]: https://github.com/odoo/odoo/commit/656cac1bf21c7c5a56aa569008aac58436c747fb
[2]: https://github.com/odoo/odoo/commit/e113bae04a64a8bd341a80736086ab7c25079dd3



opw-3031217
opw-3032482
opw-3035289

closes odoo/odoo#104156

Signed-off-by: Romain Derie (rde) <rde@odoo.com>