[docs] Tweak parameter names for fcntl module (issue 22832)

[vadmium+py at gmail.com]

https://bugs.python.org/review/22832/diff/14056/Modules/fcntlmodule.c
File Modules/fcntlmodule.c (right):

https://bugs.python.org/review/22832/diff/14056/Modules/fcntlmodule.c#newcode43
Modules/fcntlmodule.c:43: arg: object = NULL
I’m not familiar with this Clinic stuff, but is there away to make the
default appear as arg=0 rather than arg=None?

https://bugs.python.org/review/22832/diff/14056/Modules/fcntlmodule.c#newcode115
Modules/fcntlmodule.c:115: arg as ob_arg: object = NULL
Would be nice to change this to arg=0 by default too

https://bugs.python.org/review/22832/diff/14056/Modules/fcntlmodule.c#newcode332
Modules/fcntlmodule.c:332: start as startobj: object = NULL
Again the comment about len and start being documented as integers

https://bugs.python.org/review/22832/