chore: Upgrade python syntax through pyupgrade (fossasia#7326)

Author: iamareebjamal

app/api/access_codes.py

@@ -53,7 +53,7 @@ def before_create_object(self, data, view_kwargs):
                     if not ticket_object.is_hidden:
                         raise ConflictError(
                             {'pointer': '/data/relationships/tickets'},
-                            "Ticket with id {} is public.".format(ticket)
+                            f"Ticket with id {ticket} is public."
                             + " Access code cannot be applied to public tickets",
                         )
                 except NoResultFound:

app/api/admin_sales/events.py

@@ -7,7 +7,6 @@
 from app.api.helpers.utilities import dasherize
 from app.models import db
 from app.models.event import Event
-from app.models.order import Order, OrderTicket
 
 
 class AdminSalesByEventsSchema(Schema):