internal/blobstore: remove unused fixture
internal/blobstore: remove unused fixture

The httpsuite.HTTPSuite fixture wasn't
used at all and was somewhat confusing,
so we remove it.

fabricematrat/charmstore,frankban/charmstore,juju/charmstore,juju/charmstore,frankban/charmstore,juju/charmstore,frankban/charmstore,fabricematrat/charmstore,fabricematrat/charmstore