[COST-4930] drop unrequested fields from the ec2 model (#5119)

* [COST-4930] drop unrequested fields and alter instance_name in ec2 model

* separate field changes from dropping cols

koku/reporting/provider/aws/models.py

@@ -204,13 +204,11 @@ class Meta:
     usage_end = models.DateField(null=True)
     cost_entry_bill = models.ForeignKey("AWSCostEntryBill", on_delete=models.CASCADE, null=True)
     account_alias = models.ForeignKey("AWSAccountAlias", on_delete=models.PROTECT, null=True)
-    organizational_unit = models.ForeignKey("AWSOrganizationalUnit", on_delete=models.SET_NULL, null=True)
     usage_account_id = models.CharField(max_length=50, null=False)
     resource_id = models.CharField(max_length=256, null=False)
     instance_name = models.CharField(max_length=256, null=True)
     instance_type = models.CharField(max_length=50, null=True)
     operating_system = models.CharField(max_length=50, null=True)
-    availability_zone = models.CharField(max_length=50, null=True)
     region = models.CharField(max_length=50, null=True)
     vcpu = models.IntegerField(null=True)
     memory = models.CharField(max_length=50, null=True)