Remove logging debug of loaded modules

Hi there,

Would you be willing to remove this debug statement from the __init__.py file? It leads to excessive logging output. In my case, it is printing the name of ~1800 modules and really crowding out more valuable debug statements. Thanks!

https://github.com/matplotlib/matplotlib/blob/98115e9b5134f4c71dc196a56f6ed8df4737174a/lib/matplotlib/__init__.py#L1445