ident.c: replace fprintf with fputs to suppress compiler warning

ident.c: replace fprintf with fputs to suppress compiler warning

Compiling today's pu gave
    ...
    CC ident.o
    CC levenshtein.o
ident.c: In function 'fmt_ident':
ident.c:206: warning: format not a string literal and no format arguments
    CC list-objects.o
    ...

This warning seems to have appeared first in 18e95f279ec6 (ident.c:
remove unused variables) which removed additional fprintf arguments.

Suppress this warning by using fputs instead of fprintf.

Signed-off-by: Tarmigan Casebolt <tarmigan+git@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>