nvim-treesitter grammars updater: avoid silent fails

What if some grammar fails to update? Well, it gets removed from the
generated file. How would we know that the grammar failed? By reading
logs. Who reads logs if the command didn't crash? Right, nobody. Or even
if someone examines the logs, it is too easy to overlook the failure
(are you sure you read every single line of code? It is not even colored)

They are useful only in two cases:

- During debugging, this happens rarely
- Let's print something to keep the user informed that we are doing
  something

  It should not to be a mistake to overlook one line from the logs,
  because when you run the same script hundreds of times (we do updates
  weekly), you barely look at logs; you scan them, at most.

By treating logs this way, we can inform ourselves about possible
breakages before it gets even reviewed by another person, not by a user
opening a bug report months later.

![image](https://github.com/user-attachments/assets/608dad73-626a-4e06-9122-38d2a085d473)

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