builtin/remote.c: use the right kind of STRING_LIST_INIT

builtin/remote.c: use the right kind of STRING_LIST_INIT

Since 4a4b4cda (builtin-remote: Make "remote -v" display push urls,
2009-06-13), the string_list that was initialized with 0 in its
strdup_string member is immediately made to strdup its key strings
by flipping the strdup_string member to true.  When 183113a5
(string_list: Add STRING_LIST_INIT macro and make use of it.,
2010-07-04) has introduced STRING_LIST_INIT macros, it mechanically
replaced the initialization to STRING_LIST_INIT_NODUP.

Instead, just use the other initialization macro to make it strdup
the key from the beginning.

Signed-off-by: Junio C Hamano <gitster@pobox.com>