Flower store app. Part 2. Strangeness out of nowhere

While talks continue about the feasibility of an app for a flower store, I decided to just take a look - what kind of site is proposed to be embodied as an app?
Having run it through all known diagnostic tools, I found one very strange feature: the strange piece of code appears ONLY when checking it through Google's rich-results tester.
Example: look at source of this page - https://saholaflowers.com/. Screenshot of last few lines:

And now the same page, viewed through Google tools: https://search.google.com/test/rich-results/result?id=foGWPW0ALJ5aOdsWqBcjPw

Do you see a new piece of code after the closing script tag?

I'll remind you, this is source code - there can't be a dynamically added JS DOM. But this piece of code only appears when viewed through this tool.

This piece of code has the site's old domain, saholany dot com. I have checked the WHOLE site, every file, the entire database - there is not a single mention of this old domain.

I've reset all the cache on the hosting, on the site, on the browser. But this code is still there.

Not only that, if I make changes to the site code (like adding a tag with the class test-tag-for-goole), the tool will see those changes - so it's not a Google cache or some other cached value, no:

So what is that?

And even more important question, how do you clean this up? This is the first time I've encountered a situation where I can't find the reason for the code appearing on my own site....

To be continued.