Update HACKING.rst.
Update HACKING.rst.

Removes the requirement for a trailing blank line in multiline
docstrings, just before the closing '"""'.  This blank line is not
needed anymore, as the editors it was recommended for no longer
have the problem that this blank line was working around.

Change-Id: I4e532231f1d99e9f5048cbfcc791a4328fb1e8f5

n0ano/ganttclient