test_date.c: remove reference to GIT_TEST_DATE_NOW

Remove the reference to the GIT_TEST_DATE_NOW which is done in date.c.
We can't get rid of the "x" variable, since it serves as a generic
scratch variable for parsing later in the function.

Signed-off-by: Stephen P. Smith <ischis2@cox.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/helper/test-date.c

@@ -104,7 +104,6 @@ static void getnanos(const char **argv)
 int cmd__date(int argc, const char **argv)
 {
 	const char *x;
-	x = getenv("GIT_TEST_DATE_NOW");
 
 	argv++;
 	if (!*argv)