contrib/nvi: fix -w option

[fernape]

Summary

Reported in PR 241985

Compose the "window=%s" option as a CHAR_T to be processed properly in
opts_set

Test Plan

Before the patch, trying this:

$ vi -w 10

shows an error:

set: no wo0 option: 'set all' gives all option values
Press Enter to continue:

And vi launches with as many lines as to fill the terminal screen

------------ BEGINING OF SCREEN

~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
~
------------ END OF SCREEN

After the patch, thre is no error

$ vi -w 10

and the vi screen is limited to the specified amount of lines:

------------ BEGINING OF SCREEN

~
~
~
~
~
~
~
~
~
------------ END OF SCREEN

[fernape]

This one has been merged upstream

Should I withdraw this review?
What to do with the original PR?