users: Drop jQuery code as the library dependency has been removed

Closes: #2484

Tests:

- Functional tests for users app works.

- When updating the user if the delete user is not checked, delete confirmation
dialog is not shown.

- When updating the user if the delete user is checked, delete confirmation
dialog is shown. It can be dismissed and re-shown many times. When confirm
button is clicked, the form is submitted and user is deleted.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/modules/users/static/users.js

@@ -22,8 +22,6 @@
  * in this page.
  */
 
-var deleteConfirmed = false;
-
 document.addEventListener('DOMContentLoaded', (event) => {
     const form = document.querySelector('form.form-update');
     form.addEventListener('submit', onUserUpdateSubmit);
@@ -33,10 +31,12 @@ document.addEventListener('DOMContentLoaded', (event) => {
     confirmDeleteButton.addEventListener('click', () => {
         onUserDeleteConfirmed(form);
     });
-});
 
-// Show the confirmation dialog if the delete checkbox is selected
+    var deleteConfirmed = false;
-function onUserUpdateSubmit(event) {
+    const modal = new bootstrap.Modal('#user-delete-confirm-dialog');
+
+    // Show the confirmation dialog if the delete checkbox is selected
+    function onUserUpdateSubmit(event) {
         const deleteUserCheckbox = document.getElementById('id_delete');
         if (!deleteUserCheckbox.checked) {
             return;
@@ -48,13 +48,14 @@ function onUserUpdateSubmit(event) {
         }
 
         event.preventDefault();
-    $("#user-delete-confirm-dialog").modal('show');
+        modal.show();
-};
+    };
 
-// Submit the user edit form
+    // Submit the user edit form
-function onUserDeleteConfirmed(form) {
+    function onUserDeleteConfirmed(form) {
         deleteConfirmed = true;
-    $('#user-delete-confirm-dialog').modal('hide');
+        modal.hide();
         // Click instead of submit to disable the submission button
         form.querySelector('input[type=submit]').click();
-};
+    };
+});