bisect--helper: convert `*_warning` char pointers to char arrays.

Instead of using a pointer that points at a constant string,
just give name directly to the constant string; this way, we
do not have to allocate a pointer variable in addition to
the string we want to use.

Let's convert `need_bad_and_good_revision_warning` and
`need_bisect_start_warning` char pointers to char arrays.

Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Tanushree Tumane <tanushreetumane@gmail.com>
Signed-off-by: Miriam Rubio <mirucam@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/bisect--helper.c

@@ -281,11 +281,11 @@ static int mark_good(const char *refname, const struct object_id *oid,
 	return 1;
 }
 
-static const char *need_bad_and_good_revision_warning =
+static const char need_bad_and_good_revision_warning[] =
 	N_("You need to give me at least one %s and %s revision.\n"
 	   "You can use \"git bisect %s\" and \"git bisect %s\" for that.");
 
-static const char *need_bisect_start_warning =
+static const char need_bisect_start_warning[] =
 	N_("You need to start by \"git bisect start\".\n"
 	   "You then need to give me at least one %s and %s revision.\n"
 	   "You can use \"git bisect %s\" and \"git bisect %s\" for that.");