Minor inconsistency in numpy.md: text mentions tic/toc but code uses qe.Timer

[Honaminto]

In the "Implicit Multithreading" exercise section of numpy.md (Exercise 10.4, Part 2), the instructional text says:

"For this part of the exercise you can use the tic/toc functions from the quantecon library to time the execution."

But the actual code cell right below it uses qe.Timer(...) as a context manager, not tic()/toc():

with qe.Timer("Broadcasting operation"):
    B = x / y

This looks like a leftover from a previous version of the lecture, before the timing code was migrated from tic/toc to the Timer context manager. The sentence introducing the exercise should probably be updated to match the code, e.g.:

"For this part of the exercise you can use the qe.Timer context manager from the quantecon library to time the execution."

I noticed this while doing a French translation review of this lecture and wanted to flag it separately, since it's an issue with the English source rather than the translation itself.