The test for account followup use UTC time, but the default `date_maturity`
and `date_due` of an account invoice come from fields.Date.context_today`.
One failing test for project_timesheet also used `today` instead of
`context_today`.
So depending on the test user timezone, an error of one day (if UTC time
and user time are on different day) occured which failed the tests.
For example:
* user has GMT+1 timezone, test fails 0:00am–1:00am (11:00pm-0:00am in UTC)
* user has GMT+3 timezone, test fails 0:00am–3:00am (9:00pm-0:00am in UTC)
This fix removes UTC use in the tests.
Nicolas Lempereur
a5e32690b0