Upgrade gds-sso to 9.2.5

- This fixes a problem where we were seeing duplicate users created in
  Preview when we signed in to Transition, because Transition's
  database is synced to preview each night but Signon's isn't. The SSO
  gem wasn't recognising us as already having a user, but this bug was
  fixed in this later version of the gem.
- All our tests still pass, so this looks good.
Merge pull request #308 from alphagov/update_gds-sso

Upgrade gds-sso to 9.2.5
Enable users to select unresolved as a mapping type

- Add a blurb about unresolved mappings and what the point of them is,
  when the option is selected. The copy on this probably needs a work,
  and in fact I'm not even sure it needs to be here. Thoughts?
- Mappings marked unresolved added through here get added, correctly, to
  the database with a type of unresolved.
Add a note explaining what an unresolved mapping is

- The note's copy has been discussed with @fofr.
- Add this as a partial, rendered only when the unresolved dropdown is
  selected, thanks to some JavaScript, and include it in two places.
Show unresolved as archives in the mappings table, in muted style

- Add a question mark with a hover to explain the unresolved type, but
  why it is marked as an archive and greyed out.
- Based on @fofr's prototype.
Show current status when editing unresolved mappings

- Like we do for redirects and archives, and with JavaScript off.
Set mappings to unresolved by default in the MappingsFromHostPaths import