[COST-4947] Remove account and region fields from ProviderInfrastructureMap model (#5076)

Author: cgoodfred

koku/api/provider/models.py

@@ -573,5 +573,3 @@ class Meta:
 
     infrastructure_type = models.CharField(max_length=50, choices=Provider.CLOUD_PROVIDER_CHOICES, blank=False)
     infrastructure_provider = models.ForeignKey("Provider", on_delete=models.CASCADE)
-    infrastructure_account = models.CharField(max_length=50, null=True)
-    infrastructure_region = models.CharField(max_length=50, null=True)