fix: remove default namespace as a requirement to list namespaces (#3711

)

Currently Flipt with authz requires user to have read access to default
namespace in order to list the namespaces. This edge case ninja'd its way
into the code like a shadow in the night, but it’s time for this stealthy
PR troublemaker to find another codebase to haunt!

Side effect 1: the deps has been updated and the code should be regenerated.
Side effect 2: the tests are broken with PR #3595 in RPC and they are not run
in CI.