docs: Move SPDX identifiers under first title

[travier]

docs: Move SPDX identifiers under first title

Having a comment right before the first title apparently confuses
Jekyll.

Fixes: #3185

---

docs: Cleanup title for historical OSTree README

[travier]

The docs still weren't being updated as there was a rulset preventing force-pushing to the gh-pages branch. I fixed the push and re-triggered a workflow, which updated the site but the last PR I has made had an issue, thus this PR.

[travier]

This one looks good: https://travier.github.io/ostree/

[travier]

Overriding the checks here as this is a pure docs change:
/override ci/prow/fcos-e2e

[openshift-ci]

@travier: Overrode contexts on behalf of travier: ci/prow/fcos-e2e

In response to this:

Overriding the checks here as this is a pure docs change:
/override ci/prow/fcos-e2e

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[travier]

OK, we finally have a successful run and and updated, not broken website:

• https://github.com/ostreedev/ostree/actions/runs/8031591112/job/21940068611
• https://ostreedev.github.io/ostree/