Remove the scoped publish-wiki workflow and the marker path (2.0.0)

- .gitea/scoped_workflows/publish-wiki.yml is deleted
- tools/publish_wiki.py requires WIKI_PRUNE, reads no marker, and defaults
  WIKI_DIR to docs/wiki; its tests follow
- README, onboarding, troubleshooting and upgrading guides, and the wiki pages
  in English, Danish and Bahasa Malaysia no longer describe the scoped workflow
- changelog entry 2.0.0 with the Breaking group

Task: MIL-009#6
Task: MIL-009#8

.gitea/scoped_workflows/publish-wiki.yml

@@ -1,48 +0,0 @@
-name: Publish wiki
-
-# DEPRECATED (ADR-0009, MIL-008): repositories publish their wiki by calling
-# the reusable workflow publish-wiki-pages.yml. This scoped workflow stays
-# until every repository that has wiki/.publish has migrated; it is then
-# removed in a later major release.
-
-# Shared through scoped delivery: it runs in every repository of an
-# organization, but writes only where the repository has opted in with
-# wiki/.publish (ADR-0004). TOKEN_FOR_GITEA_WIKI is read from the organization
-# secrets; there is no fallback to the read-only sync token. The script is a
-# file of TirSystem/github-action (tools/publish_wiki.py), fetched with a
-# second checkout so that it is readable, lintable and tested as a file
-# (MIL-004 task 6).
-on:
-  push:
-    branches: [ main ]
-    paths:
-      - "wiki/**"
-  workflow_dispatch:
-
-concurrency:
-  group: publish-wiki
-  cancel-in-progress: false
-
-jobs:
-  publish-wiki:
-    permissions:
-      contents: read
-    runs-on: ubuntu-latest
-    timeout-minutes: 10
-    steps:
-      - name: Check out the repository
-        uses: actions/checkout@v4.2.2
-
-      - name: Fetch the shared script
-        uses: actions/checkout@v4.2.2
-        with:
-          repository: TirSystem/github-action
-          ref: v1
-          path: shared-scripts
-
-      - name: Publish the pages to the wiki
-        env:
-          GITEA_API_URL: ${{ gitea.api_url }}
-          SOURCE_REPOSITORY: ${{ gitea.repository }}
-          WIKI_CREDENTIALS: ${{ secrets.TOKEN_FOR_GITEA_WIKI }}
-        run: python3 shared-scripts/tools/publish_wiki.py