sigrok-cli: Fix memory leak if we save the default output format to a file.

g_free_byte_array accepts as the second argument a gboolean which determines if
the actual byte data should also be freed:
	https://developer.gnome.org/glib/2.28/glib-Byte-Arrays.html#g-byte-array-free

If we pass a FALSE here the data should be freed with g_free(), instead just
pass TRUE and the data will be automatically freed.