[MM-47824] fix promoteGuestToUserCmdF to handle the proper errors (#26397)

Co-authored-by: Mattermost Build <build@mattermost.com>

server/cmd/mmctl/commands/user_e2e_test.go

@@ -928,7 +928,7 @@ func (s *MmctlE2ETestSuite) TestPromoteGuestToUserCmd() {
 		printer.Clean()
 
 		err := promoteGuestToUserCmdF(c, nil, []string{user.Email})
-		s.Require().Nil(err)
+		s.Require().NoError(err)
 		defer s.Require().Nil(s.th.App.DemoteUserToGuest(s.th.Context, user))
 		s.Require().Len(printer.GetLines(), 1)
 		s.Require().Len(printer.GetErrorLines(), 0)
@@ -938,7 +938,7 @@ func (s *MmctlE2ETestSuite) TestPromoteGuestToUserCmd() {
 		printer.Clean()
 
 		err := promoteGuestToUserCmdF(s.th.Client, nil, []string{user.Email})
-		s.Require().Nil(err)
+		s.Require().Error(err)
 		s.Require().Len(printer.GetLines(), 0)
 		s.Require().Len(printer.GetErrorLines(), 1)
 		s.Require().Equal(fmt.Sprintf("unable to promote guest %s: You do not have the appropriate permissions.", user.Email), printer.GetErrorLines()[0])