Update dataset upload description

app/server/templates/admin/dataset_upload.html

@@ -20,14 +20,14 @@
           <b>To annotate texts, you first need to import a set of text items to annotate it.</b>
         </p>
         <p>
-          Each item should contain a text.
+          Each line should contain a text.
         </p>
         <form action="" method="post" enctype="multipart/form-data">
           {% csrf_token %}
           <div class="section">
             <div class="control">
               <label class="radio" style="margin-bottom:10px;">
-                <input type="radio" name="format" checked> Upload a CSV file from your computer
+                <input type="radio" name="format" checked> Upload a TXT file from your computer
               </label>
               <div class="file is-small" style="margin-bottom:20px;">
                 <label class="file-label">