This commit fixes an issue that was making it impossible to clear filters in the "Filter products by attribute" widget when the attribute name contained non-ASCII characters. The problem was caused by a call to sanitize_title() which doesn't seem necessary as it is sanitizing one of the widget parameters which is already sanitized in 679d719368/includes/widgets/class-wc-widget-layered-nav.php (L116). So this commit simply removes the sanitize_title() call. Even if we needed to sanitize the variable `$taxonomy`, it would be better to use sanitize_text_input_field() or wc_sanitize_taxonomy_name() as sanitize_title() will replace accented characters.
For more about the problem that is fixed by this commit see #21028
20fd569a55