jenkins: use git credentials

Jenkinsfile

@@ -57,6 +57,7 @@ pipeline {
                                 stage('Push updates') {
                                     steps {
                                         dir("fdroid-repo") {
+                                            withCredentials([gitUsernamePassword(credentialsId: '3563e7c8-6a79-407c-9681-5d6e6291ba34')]) {
                                                 sh '''
                                                     git fetch origin
                                                     git cehckout master
@@ -72,6 +73,7 @@ pipeline {
                             }
                         }
                     }
+                }
                 stage('Web') {
                     stages {
                         stage('Build') {