Retire internal Static Docs build wiring (#23128)

Summary:

Remove the unused buck based static docs. The independent docs.pytorch.org/executorch workflow continues to publish the public docs.

Authored with AI assistance from Codex.

Reviewed By: shoumikhin, JacobSzwejbka

Differential Revision: D121631025

Pull Request resolved: #23128

Author: JakeStevens