windows: removed duplicate termwidth definition
Changeset
dbf91976f900 caused this when the "from win32 import *" line
was replaced with explicit import statements: the wildcard import was
at the bottom of the file and so windows.termwidth was overwritten by
win32.termwidth as indented, but the new explicit import statements
were at the top and so win32.termwidth got lost.
With the switch to ctypes, win32 can always be imported and so the
fallback termwidth in windows is no longer needed.