fix using the emailext plugin incorrectly

vars/buildTestDeploy.groovy

@@ -96,7 +96,8 @@ def call(ArrayList<String> dependencyList, String gitUrl='',
     } // end stages
     post {
       failure {
-        emailext body: '$DEFAULT_CONTENT', recipientProviders: [env.RECIPIENT_LIST, brokenTestsSuspects(), brokenBuildSuspects(), developers()], subject: '[Jenkins] $DEFAULT_SUBJECT'
+        emailext body: '$DEFAULT_CONTENT', recipientProviders: [brokenTestsSuspects(), brokenBuildSuspects(), developers()], subject: '[Jenkins] $DEFAULT_SUBJECT', to: env.RECIPIENT_LIST
+        mattermostSend
       }
       always {
         node('Docker') {