[docs] Sync-up docstrings in C version of the the decimal module (issue 27779)

[stefan at bytereef.org]

https://bugs.python.org/review/27779/diff/18450/Modules/_decimal/docstrings.h
File Modules/_decimal/docstrings.h (right):

https://bugs.python.org/review/27779/diff/18450/Modules/_decimal/docstrings.h#newcode244
Modules/_decimal/docstrings.h:244: Represents the number as a triple
tuple, to show the internals exactly as\n\
I meant "show the internals exactly as they are". This is not true for
the C version.

It is not true for the Python version because it uses a string for the
coefficient -- the initial version had the tuple IIRC.

https://bugs.python.org/review/27779/