2023.2 Spec display problem

[Ai Hamano]

The 2023.2 Spec is not displayed correctly on the Tacker Spec site below.
  - https://specs.openstack.org/openstack/tacker-specs/

This is because promote-openstack-specs was changed to not be executed in tacker-specs's Zuul job before the 2023.2 spec was posted.
  - https://opendev.org/openstack/project-config/src/branch/master/zuul.d/jobs.yaml#L290-L303

This problem can be resolved by adding the process equivalent to the promote-openstack-specs job to tacker-specs's Zuul job.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/tacker-specs/+/896185

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/tacker-specs/+/896185
Committed: https://opendev.org/openstack/tacker-specs/commit/da42f39961942e876785f4ee9a27992d06640186
Submitter: "Zuul (22348)"
Branch: master

commit da42f39961942e876785f4ee9a27992d06640186
Author: Ai Hamano <email address hidden>
Date: Fri Sep 22 15:03:57 2023 +0900

    Fix the display problem of 2023.2 Specs

    This patch adds processing equivalent to the promote-openstack-specs
    job to the tacker-spec's Zuul job and fixes the display problem of
    2023.2 Specs[1].

    Also, change the sphinx extension "sphinxcontrib.plantuml" to
    "sphinxcontrib.mermaid" to eliminate the dependency on Java
    in the build environment.

    [1] https://specs.openstack.org/openstack/tacker-specs/

    Closes-Bug: #2037035
    Change-Id: I82a1e549b51669e82d10daaad4378f7a049cf95a