docs: Remove coroutine/DPP_CORO experimental warnings

[DJOetzi]

Removed notices of coroutines being an experimental feature.

Documentation change checklist

• [x] My documentation changes follow the docs style guide and any code examples follow the coding style guide.
• [x] I tested that my change works before raising the PR (via running doxygen, and testing examples).
• [x] I have not moved any existing pages or changed any existing URLs without strong justification as to why.
• [x] I have not generated content using AI or a desktop utility such as grammarly.

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[Jaskowicz1]

Any update on this?

[DJOetzi]

You're missing

https://github.com/brainboxdotcc/DPP/blob/ced36fd7652ed24ec3784cbc150722a1e5f6456a/include/dpp/coro/job.h#L48

https://github.com/brainboxdotcc/DPP/blob/ced36fd7652ed24ec3784cbc150722a1e5f6456a/include/dpp/coro/async.h#L103

https://github.com/brainboxdotcc/DPP/blob/ced36fd7652ed24ec3784cbc150722a1e5f6456a/library/CMakeLists.txt#L292

(just remove the word "experimental" here, keep the message()). https://github.com/brainboxdotcc/DPP/blob/ced36fd7652ed24ec3784cbc150722a1e5f6456a/include/dpp/coro/task.h#L87

https://github.com/brainboxdotcc/DPP/blob/ced36fd7652ed24ec3784cbc150722a1e5f6456a/include/dpp/coro/coroutine.h#L67

should I just remove these comments altogether?