Add run permission for download dataset script

Jenkinsfile

@@ -28,6 +28,7 @@ node {
         withEnv(["KAGGLE_USERNAME=${params.KAGGLE_USERNAME}",
               "KAGGLE_KEY=${params.KAGGLE_KEY}","CUTOFF=${params.CUTOFF}"]) {
             sh 'echo KAGGLE_USERNAME: $KAGGLE_USERNAME'
+            sh "chmod u+x ./download_dataset.sh"
             sh "./download_dataset.sh $CUTOFF"
         }
     }