search: if not specified, set archived:no by default

Created by: rvantonder

As in title. It is weird to me that the options in ReposListOptions imply negation of the property (NoForks, NoArchived), and I suppose this was because it was easy to fall back to false default values in tests and stuff. Consequently, now that NoArchived should be set to true by default, all the tests where it matters must add it explicitly.

There are ways to improve this, but I would rather not invest time refactoring here because I look forward to not doing it this way and using a select instead https://github.com/sourcegraph/sourcegraph/issues/7003.

Tests updated. Looks like we don't have e2e test for this :/. So I'll add one before merging but putting up fo review now.