The `test_calendar_month_view_start_hour_displayed` makes sure
that start hour is display in calendar month view.
The test was failing because when clicking on scale selector,
it used '.dropdown-toggle:contains("Week")' however it might
happen that the current scale is not week.
This commit fixes this issue by changing the way we access
the scale selector.
fixes runbot-59023
closes odoo/odoo#156121
Signed-off-by: Arnaud Joset (arj) <arj@odoo.com>