In your inbox, when you are assigned to a task then you receive mail from
the project. In that mail, the mail subject and body are shown in one line.
In this commit, The mail template's "assignee_name" field currently has a 'span'
tag, which may cause inline subject and body issues. To prevent this, it is
recommended to use a 'div' tag instead.
task-3274690
closesodoo/odoo#118576
Signed-off-by: Xavier Bol (xbo) <xbo@odoo.com>