The `__future__` we relied on is now, where the 3 specific things are
all included [since Python 3.0](https://docs.python.org/3/library/__future__.html):
* absolute_import
* print_function
* unicode_literals
* division
These import statements are no-ops and are no longer necessary.
Previously, this was done by hand in the coverage-generate-data script. Lets
formalize this into a preset.
I am trying to see if with a slight bit of work I can get coverage working again
since it will help me write SILGen tests.
