Disable GitHub Pages publishing

# Disable GitHub Pages publishing

## Action

Repo Settings → Pages → Source: **None**.

Requires repo admin.

## Why

The mkdocs site generator and its publish workflow were removed in #733 (docs-cleanup), which was merged into `develop` as part of the modernization chain on 2026-05-07. Nothing rebuilds the site anymore, but the existing `gh-pages` branch is still serving stale content at https://hackforla.github.io/CivicTechJobs/.

Canonical docs are now flat markdown under [`docs/`](https://github.com/hackforla/CivicTechJobs/tree/develop/docs). Contributors hitting the Pages URL read out-of-date content while the truth has moved, so we need to remove the actual pages.

## Scope

1. Settings → Pages → Source: None.
2. Optional: delete the `gh-pages` branch once Pages is off.

## Out of scope

- No code changes. No PR.
- External references to the old site URL were already updated in CONTRIBUTING.md, README.md, and the issue templates as part of the docs-cleanup work — nothing breaks when the site goes dark.

## Owner

Repo admin.