Redundant elements in Finder Schema

[GDSNewt]

I was documenting the finder schema and found a few things that seem redundant/not-utilised.

1. I'm wondering if we can remove "search" as a document type. Initially, "search" was specified as a document type to ensure the advanced search finder wasn't indexed. By giving it this document type, we could prevent the /search/advanced finder from being indexed. However, it appears that this finder is no longer in use, as indicated by this commit.

2. 'No_index'. I was only able to find one instance of this property being used. It also seems like it was only used for Brexit, so I'm wondering if it is still relevant.

3. 'Generic_description'. The only trace I could find of this in use was in this commit, in which it is being removed. It looks like it was used for Brexit, so I again am wondering if we still need it.

4. 'Logo_path'. It doesn't appear that this property is widely used, it was introduced in this PR from 2015. I assume this is very outdated now, so again i'm wondering if we can get rid.

5. 'Canonical_link'. This one again looks outdated, and doesn't seem widely used.