[FIX] web_editor: restore avoiding updates of link content

[1] mistakenly removed the variable used by the mechanism that was
introduced in [2] to avoid updating link content.

This commit uses the link's `needLabel` instead to achieve the same
goal.

Steps to reproduce:
- Add a mega menu.
- Set the mega menu template to Cards.
- Click on the text of a card.
- DO NOT click on the edit link icon in the popover.
- Click on the href field in the options panel.
- Change the value.

=> Links content was broken (image was removed and texts were grouped).

[1]: https://github.com/odoo/odoo/commit/75166dbcd4962f30624fe19829757acbf8e76022
[2]: https://github.com/odoo/odoo/commit/7a0e58f8d7237514d23d815cdf3d81fc79edb1ec

task-3300977

X-original-commit: 1dbcf2825b2d495c206e110a39efe620e646e7c4
Part-of: odoo/odoo#121362

addons/web_editor/static/src/js/wysiwyg/widgets/link.js

@@ -508,7 +508,7 @@ const Link = Widget.extend({
      * @param {boolean} force
      */
     _updateLinkContent($link, linkInfos, { force = false } = {}) {
-        if (force || (linkInfos.content !== this.data.originalText || linkInfos.url !== this.data.url)) {
+        if (force || (this.needLabel && (linkInfos.content !== this.data.originalText || linkInfos.url !== this.data.url))) {
             if (linkInfos.content === this.data.originalText) {
                 $link.html(this.data.originalHTML);
             } else if (linkInfos.content && linkInfos.content.length) {