[FIX] website: fix traceback when saving anchor with unchanged name

Since commit [1], anchor dialog is now in OWL. During adaptation, a line
of code was forgotten which lead to a traceback when an anchor is saved
with an unchanged name.

Steps to reproduce:

- Drop a Text-Image snippet and set an anchor on it.
- On the anchor notification, click on "Edit"
- In the dialog, do not modify the anchor name (or change it but then
  set the original one again)
- Click on "Save & Copy"
=> Traceback

[1]: https://github.com/odoo/odoo/commit/57ed8bc0bf9d1ae2b7542d677a4d7e8fd1899ea2

task-3576975

closes odoo/odoo#141936

Signed-off-by: Soukéina Bojabza (sobo) <sobo@odoo.com>

addons/website/static/src/js/editor/snippets.options.js

@@ -2749,8 +2749,7 @@ options.registry.anchor = options.Class.extend({
                 if (this.$target[0].id === anchorName) {
                     // If the chosen anchor name is already the one used by the
                     // element, close the dialog and do nothing else
-                    this.close();
-                    return;
+                    return true;
                 }
 
                 const alreadyExists = !!this.ownerDocument.getElementById(anchorName);