Edit button not showing, how to remove block

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I recently added this javascript code through using a HTML block to my main page.

<script src="https://scheduler.groupon.com/booking/widget.js"></script><script>GRPNSCH.addBooker({ booking_key: '564e8a8e98614d1af487d922d418ae4fa7766218' });</script>

Problem is I believe it has caused an error, and now the edit button is not showing on the main page. It shows on the other pages where the block doesn't exist. How do I remove this block/code when there isn't an edit button? I'm sure the solution is simple, but I've only built the site using the edit function/ button on the site, I don't know the other way. Please walk me through it.

Website: rpmautomotivecanada.com