[FIX] removing redefinition of datetime module

[jiaulislam]

Currently at version 16.0.1.0.0 in the model/crm_dashboard.py datetime module is getting import 2 times.

Before:

import datetime
import calendar

from odoo import models, fields, api from odoo.tools import date_utils from odoo.http import request

from dateutil.relativedelta import relativedelta from datetime import datetime

> After:

import calendar

from odoo import models, fields, api from odoo.tools import date_utils from odoo.http import request

from dateutil.relativedelta import relativedelta from datetime import datetime

[jiaulislam]

@CybroOdoo Could you please look into the PR?