If you want only your own Google Tag Manager container to run on your site, the HomeRunner GTM container can be switched off on request.
Why you cannot remove it yourself. The HomeRunner GTM container is loaded by the HomeRunner plugin itself rather than pasted into the theme, so it cannot be deleted from a GTM account directly. Removal is done in WordPress by the support team.
What happens to your tracking. Removing it does not affect your own tracking. Your GTM container, GA4, and ads tags load independently. The booking engine continues pushing standard ecommerce events (view_item, begin_checkout, purchase, and others) to the dataLayer, and your own container can read these events and forward them to your analytics.
Contact support to request the removal for your site.