Minor: Fix display in form to add users to class

public/main/admin/add_users_to_usergroup.php

@@ -382,8 +382,10 @@ echo Display::input('hidden', 'form_sent', '1');
 echo Display::input('hidden', 'add_type', null);
 
 ?>
-<div class="row">
+<table border="0" cellpadding="5" cellspacing="0" width="100%">
-    <div class="col-md-5">
+    <tbody>
+        <tr>
+            <td width="40%" align="center">
                 <?php if (Usergroup::SOCIAL_CLASS == $data['group_type']) {
                     ?>
                     <select name="relation" id="relation">
@@ -400,7 +402,7 @@ echo Display::input('hidden', 'add_type', null);
                             <?php echo get_lang('Human Resources Manager'); ?></option>
                     </select>
                     <?php
-} ?>
+                } ?>
 
                 <div class="multiple_select_header">
                     <b><?php echo get_lang('Users on platform'); ?> :</b>
@@ -433,8 +435,8 @@ echo Display::input('hidden', 'add_type', null);
                     } ?> onchange="checked_in_no_group(this.checked);" name="user_with_any_group" id="user_with_any_group_id">
                     <?php echo get_lang('Users registered in any group'); ?>
                 </label>
-    </div>
+            </td>
-    <div class="col-md-2">
+            <td width="20%" align="center">
                 <div style="padding-top:54px;width:auto;text-align: center;">
                     <button class="btn btn--plain" type="button" onclick="moveItem(document.getElementById('elements_not_in'), document.getElementById('elements_in'))" onclick="moveItem(document.getElementById('elements_not_in'), document.getElementById('elements_in'))">
                         <i class="mdi mdi-fast-forward-outline ch-tool-icon"></i>
@@ -444,8 +446,8 @@ echo Display::input('hidden', 'add_type', null);
                         <i class="mdi mdi-rewind-outline ch-tool-icon"></i>
                     </button>
                 </div>
-    </div>
+            </td>
-    <div class="col-md-5">
+            <td width="40%" align="center">
                 <div class="multiple_select_header">
                     <b><?php echo get_lang('Users in group'); ?> :</b>
                 </div>
@@ -463,12 +465,18 @@ echo Display::input('hidden', 'add_type', null);
                     false
                 );
                 ?>
-    </div>
+            </td>
-</div>
+        </tr>
-<?php
+        <tr>
+            <td colspan="3" align="center">
+                <?php
                 echo '<button class="btn btn--primary" type="button" value="" onclick="valide()" ><em class="fa fa-check"></em>'.
                     get_lang('Subscribe users to class').'</button>';
-?>
+                ?>
+            </td>
+        </tr>
+    </tbody>
+</table>
 </form>
 <script>
 function moveItem(origin , destination) {