t-ctype: simplify EOF check

t-ctype: simplify EOF check

EOF is not a member of any character class.  If a classifier function
returns a non-zero result for it, presumably by mistake, then the unit
test check reports:

   # check "!iseof(EOF)" failed at t/unit-tests/t-ctype.c:53
   #       i: 0xffffffff (EOF)

The numeric value of EOF is not particularly interesting in this
context.  Stop printing the second line.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>