Hello,

I found that Org entries containing markdown source blocks don't get
properly folded on the main development branch, when markdown-mode is
also loaded.

To reproduce:

1. Download markdown-mode from MELPA or Github. [1]
2. Fix the paths in the attached init.el.
3. emacs -Q -l init.el test.org
4. Shift-tab to collapse the visibility

Output should look like this:

* Headline 1...

But instead I observe this:

* Headline 1... ```
... ```
...

If markdown-mode isn't loaded, then the problem goes away. I think the
problem might have to do with the fontification that markdown-mode
applies to the back-quoted code block.

Versions:
GNU Emacs 28.1 (build 2, x86_64-pc-linux-gnu, X toolkit, cairo version 1.17.6, Xaw3d scroll bars) of 2022-07-10
Org mode version 9.5.4 (release_9.5.4-717-g9cc60d @ /home/jack/dev/org-mode/lisp/)

[1] https://github.com/jrblevin/markdown-mode