Before this PR, when moving the snippet's position, `d-none` gets added
which should not.

With this PR, removing the `this.$target.addClass('d-none')` from
`cleanForSave` method as it was adding `d-none` unnecessarily while
moving snippets position. The fact is snippet will be hidden if the
current user has no access to the mail group. So that case will be
handled using controllers route `/group/is_member`, if this return email
of the user, snippet is visible else the user has no access to the mail
group so we remove the snippet.

task-3107451

closes odoo/odoo#126712

X-original-commit: 9b39c52e
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>
Co-authored-by: qsm-odoo <qsm@odoo.com>