Commit e6dfcd3 ("fix: use separate http client for non-github hosts")
renamed verification.SigstoreConfig.HttpClient to ExternalHttpClient,
added an external *http.Client argument to api.NewLiveClient, and added
the corresponding Factory.ExternalHttpClient field. It updated the
non-tagged unit tests but missed every //go:build integration file in
pkg/cmd/attestation/..., which broke trunk CI (build (ubuntu-latest)
and build (macos-latest) in the Unit and Integration Tests workflow):

- pkg/cmd/attestation/verification and pkg/cmd/attestation/verify
  failed to build (unknown field HttpClient; not enough arguments in
  call to api.NewLiveClient).
- TestNewInspectCmd_PrintOutputJSONFormat panicked because the
  cmdutil.Factory literal it builds did not set ExternalHttpClient,
  so the new f.ExternalHttpClient() call in inspect.go dereferenced
  a nil func value.

Rename the field at the integration-test call sites, pass
http.DefaultClient as the new external client to api.NewLiveClient,
and populate ExternalHttpClient on the inspect test factory. No
production code changes.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>