In the `slide.channel`, description field was converted from Text type
to HTML(see commit[1]). This field is also used as a description of the
`hr.resume.line` model. However the later one expects plaintext value
but gets the HTML. This leads to displaying HTML tags to the users.

With this commit, we convert description of the `slide.channel` into
plaintext before adding it as a description of `hr.resume.line`.

commit[1] - https://github.com/odoo/odoo/commit/6d914c005183aa5ae69650e3002a5a85ca83b4a6



taskID-2711308

closes odoo/odoo#81457

X-original-commit: f8eaf7b6
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>