You're changing from http to https would have nothing to do with the detection, that is handled by your host, it either supports the more secure https or not.
You were getting this alert before you changed.
After you blocked it I corrected the http address to https but it remains blocked
As I mentioned you should also speak to blogspot.com
You can also try using the - Reporting a Possible False Positive File or Website -
https://www.avast.com/false-positive-file-form.php.
You should get a response in a day or two.
However, if the underlying problem still exists it would still be blocked.
Quitting Avast wouldn't be productive, you might be able to access your blog, but any other Avast users trying to visit your blog would still get the alert.