Sorry for any confusion.
Now we know you want to remove your own block on the site, it isn’t that difficult if you know where to look. Check the avastUI > Settings > Active Protection > Web Shield - click the Sprocket icon (settings) > Site Blocking and see if the site you blocked is in that list - if so delete it from the list.

You adding a site to the block list is only on your system. Depending on your settings if you participate in the avast community then anonymous information may (as an avast user, I can’t say for sure) be passed to avast relating to the block. Before any further action is taken it would be investigated and it may also require multiple other reports from avast users blocking it before it would be added to the malicious sites list.