`no-highlight` language superseded

```html
WARN: Could not find the language 'no-highlight', did you forget to load/include a language module?
WARN: Falling back to no-highlight mode for this block.
fastlane release
```

_(yes I also find the console wording like this hilarious…)_


`no-highlight` is an old class, today I think it's `nohighlight` for hljs, not sure if it changes anything regarding md output or css styling…
_(but has to be passed as `class=nohighlight` not `class=language-nohighlight` anyways…)_

There are a lot of occurrences: [[search](https://github.com/search?q=repo%3Afastlane%2Fdocs%20no-highlight&type=code)]


most of which would use a `sh` grammar and be rid of it, while some could use a `plaintext` maybe, so the block is still styled the same as any hljs code fence.

I can proceed and fix this, selecting the best grammar one by one for what's in the repo here, and then peek around fastlane/fastlane about the autogenerated content… if there's any interest in this.