Another unused function argument in sched.c

["Jun T." <takimoto-j@xxxxxxxxxxxxxxxxx>]

In function schedaddtimed(time_t t) (Src/Builtins/sched.c, line 61)
the argument 't' is not used.

When this function is called (4 times in this file), the argument is
always equal to schedcmds->time, so the function should work fine.

But it would better to either modify line 72 to use 't',
or remove the argument from the function.
# I don't know which is better.