MM-18290 Using structured logging in file "security_update_che… (#12123)

* Refactor to use structured logging

* Properly formatted with gofmt

app/security_update_check.go

@@ -4,7 +4,6 @@
 package app
 
 import (
-	"fmt"
 	"io/ioutil"
 	"net/http"
 	"net/url"
@@ -114,7 +113,7 @@ func (s *Server) DoSecurityUpdateCheck() {
 					}
 
 					for _, user := range users {
-						mlog.Info(fmt.Sprintf("Sending security bulletin for %v to %v", bulletin.Id, user.Email))
+						mlog.Info("Sending security bulletin", mlog.String("bulletin_id", bulletin.Id), mlog.String("user_email", user.Email))
 						license := s.License()
 						mailservice.SendMailUsingConfig(user.Email, utils.T("mattermost.bulletin.subject"), string(body), s.Config(), license != nil && *license.Features.Compliance)
 					}