Fix listing type default value (#2796)

Fix listing type default value (#2796)

* Fix listing type default value

The listing type parameter is only meant for the frontpage, but is
also applied inside of communities. The result is that this call
returns nothing, because it defaults to ListingType::Local:
https://fedibb.ml/api/v3/post/list?community_id=3

It needs to be called like this to get any posts:
https://fedibb.ml/api/v3/post/list?community_id=3&type_=All

This is clearly not expected behaviour, when a community is
specified, the listing type should default to All.

* fix clippy