[FIX] mail: fix alignement for chatter in window

Before this commit:

For chatter in window, the name of the record is not in an appropriate place in
header as there is an empty space before name.

After this commit:

The name of the record is aligned to the left, and there is no empty space
before the name.

LINKS

Task- 2442652
PR https://github.com/odoo/odoo/pull/65600



closes odoo/odoo#65600

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>