Expand troubleshooting guide with typical error when creating groups/users on the Account level (#2338)

Author: alexott

docs/guides/troubleshooting.md

@@ -115,3 +115,8 @@ You can get this error during provisioning of the Databricks workspace.  It aris
 ## Error: 'strconv.ParseInt parsing "...." value out of range' or "Attribute must be a whole number, got N.NNNNe+XX"
 
 This kind of errors happens when the 32-bit version of Databricks Terraform provider is used, usually on Microsoft Windows.  To fix the issue you need to switch to use of the 64-bit versions of Terraform and Databricks Terraform provider.
+
+## Error: cannot create xxxx: HTTP method POST is not supported by this URL
+
+This error may appear when creating Databricks users/groups/service principals on Databricks account level when no `account_id` is specified in the provider's configuration.  Make sure that `account_id` is specified & has a correct value.
+