setterm: remove dead code [coverity scan]

Signed-off-by: Karel Zak <kzak@redhat.com>

term-utils/setterm.c

@@ -282,8 +282,6 @@ static int parse_blank(char **argv, char *optarg, int *optind)
 			errx(EXIT_FAILURE, _("argument error: %s"), arg);
 		return ret;
 	}
-	/* should be impossible to reach */
-	abort();
 }
 
 static int parse_powersave(const char *arg)