Updating blogs list

[mujina93]

All linked blogs have little content and stopped blogging in 2018 (median). Richard's Tech Notes doesn't exist anymore. Only https://www.datainmotion.dev/ is still active, even if it doesn't always blog about NiFi.

I would propose to purge the blogs list and to leave only the active ones, or at least to mark the active ones, putting them on top (in this case, it would be just https://www.datainmotion.dev/ ), so that the list of resources is more useful and doesn't require people to scour through lots of links that bring to dead ends.

(Great aggregation of resources, by the way! I understand it's not easy to come up with such lists on topics that are not mainstream)