Summary:
This applies the formatting changes from black v21.4b2 to all covered
projects in fbsource. Most changes are to single line docstrings, as black
will now remove leading and trailing whitespace to match PEP8. Any other
formatting changes are likely due to files that landed without formatting,
or files that previously triggered errors in black.

Any changes to code should be AST identical. Any test failures are likely
due to bad tests, or testing against the output of pyfmt.

Reviewed By: thatch

Differential Revision: D28204910

fbshipit-source-id: 804725bcd14f763e90c5ddff1d0418117c15809a