How do I delete a user from the master database when the user has been deleted from the Server Logins using the SSMS Object Explorer

I am using an Azure SQL Database. I deleted some users from a Azure SQL database after I saw them mentioned in a Vulnerability Assessment report. Here’s how I deleted them:

  1. Log in to SSMS
  2. Expand the Object Explorer tree
  3. Expand the ‘Security’ folder
  4. Expand the ‘Logins’ folder
  5. Highlight the user
  6. Right-click and select ‘Delete’

I went back to the Vulnerability Assessment blade and ran a new ‘Scan’ but the users I deleted still show up in the list. The list included SQL code to show that my users still exist. I ran that code back in SSMS in the master database and confirmed my users still exist. Here’s the relevant code:

SELECT * FROM sys.database_principals

When I run the following code, I get an error saying the user does not exist (‘or you do not have permission’ – but I am a server admin so I ruled that out):

DROP LOGIN <username>

How do I get rid of these logins?