The original `test.py` code, see
c2376e5cea/test/test.py,
did not have any timeout logic for TTX, but it got introduced when
`test.py` was ported from Python to JavaScript as `test.js` in
c2376e5cea (diff-a561630bb56b82342bc66697aee2ad96efddcbc9d150665abd6fb7ecb7c0ab2f).
However, I don't think we've ever actually seen TTX timing out.
Moreover, back then we used a very old version of TTX and ran the font
tests on the bots (where a hanging process would block other jobs and
would require a manual action to fix), so this code was most likely
only included defensively.
Fortunately, nowadays it should not be necessary anymore because we use
the most recent version of TTX (which either returns the result or
errors out, but isn't known to hang on inputs) and we run the font tests
on GitHub Actions which doesn't block other jobs anymore and also
automatically times the job out for us in the unlikely event that a hang
would ever occur.
In short, we can safely remove this logic to simplify the code and to get
rid of a callback.
64065141b6