chg: disable magic admin username

This feature allowed users to authenticate with any valid key and get an admin console even if they did not have admin access! 
You must now use a valid username/publickey combination to get console access (even if you don't have admin)

pkg/bastion/ssh.go

@@ -50,7 +50,7 @@ func (c authContext) userType() userType {
 	switch {
 	case c.inputUsername == "healthcheck":
 		return userTypeHealthcheck
-	case c.inputUsername == c.user.Name || c.inputUsername == c.user.Email || c.inputUsername == "admin":
+	case c.inputUsername == c.user.Name || c.inputUsername == c.user.Email:
 		return userTypeShell
 	case strings.HasPrefix(c.inputUsername, "invite:"):
 		return userTypeInvite