Re: [PATCH 2/8] builtin/gc: make `too_many_loose_objects()` reusable without GC config

Patrick Steinhardt [off-list ref] writes:

To decide whether or not a repository needs to be repacked we estimate
the number of loose objects. If the number exceeds a certain threshold
we perform the repack, otherwise we don't.

This is done via `too_many_loose_objects()`, which takes as parameter
the `struct gc_config`. This configuration is only used to determine the
threshold. In a subsequent commit we'll add another caller of this
function that wants to pass a different limit than the one stored in
that structure.

Refactor the function accordingly so that we only take the limit as
parameter instead of the whole structure.

Trivially correct and makes perfect sense.