Code snippet rendering issue since markdeep 1.18

Markeep recent update broke the code snippets of this documentation.
To be more precise, this happend in version [1.18](https://github.com/morgan3d/markdeep/releases/tag/01.18).
While undocumented, this breaking change actually enforces what [the specs mentions](https://casual-effects.com/markdeep/demodoc.md.html#basicformatting/codeblocks):

> Set off large blocks of code using **equal-length** strings of tilde ~ or back-tick ` characters.

Unfortunately, the documentation pages here are using a non-equal length, for example:

https://github.com/googlesamples/android-custom-lint-rules/blob/ee6c2faf8c9ffb821fbf0a90a32b60f027dd98a7/docs/checks/AaptCrash.md.html#L43-L52

It is as if it tries to use the same length, but **including** the language markers.

And this produces an erroneous output that can break the page rendering even more:

I'll prepare a PR to fix this globally.