kernel: cleanup vararg argument names

[fingolfin]

The kernel automatically adds the ... so we don't have to do it.

Before:

gap> Print;
function( arg...... ) ... end

After

gap> Print;
function( arg... ) ... end

Since this is a purely cosmetic triviality I am not bothering
to add a test.

[ThomasBreuer]

Nice.
It fixes also Print( Print ), which was even uglier:

Before:

gap> Print( Print );
function ( arg\.\.\.... )
    <<kernel code>> from src/streams.c:Print
end

After:

gap> Print( Print );
function ( arg... )
    <<kernel code>> from src/streams.c:Print
end