False-negative checks on a rare content

[drew2a]

How to reproduce:

1. Open Tribler
2. Check the content of fma_medium_april channel (the content will be mostly "red")
3. Try to download the red content
4. The content will be downloaded successfully

I see the described behavior on my test channel, but at the same time, I see this behavior on the content in other channels.

[ichorid]

DHT checks are unreliable. Good luck fixing this! 🍀

[drew2a]

We added a tooltip (here #7286) that shows the time of the last check and figured out that most of the health is pretty outdated.
Thus, the main cause of this issue may not be unreliable DHT checking, but incorrect health information.

[drew2a]

Fixed by @kozlovsky in #7286