Add branch condition to Discord notification stage

Previously, the Discord notification was sent for all branches. Now, the notification will only be sent for builds on the 'main' or 'master' branches, reducing unnecessary notifications.

Jenkinsfile

@@ -55,6 +55,10 @@ pipeline {
             }
         }
         stage('discord') {
+            when {
+               branch 'main'
+               branch 'master'
+            }
             steps {
                 discordSend description: "Build: ${BUILD_NUMBER}", showChangeset: true, result: currentBuild.currentResult, title: currentBuild.fullProjectName, webhookURL: env.discordwebhook
             }