Reuse TOKEN_FOR_GITEA for the wiki when TOKEN_FOR_GITEA_WIKI is absent

The Publish wiki workflow now reads secrets.TOKEN_FOR_GITEA_WIKI ||
secrets.TOKEN_FOR_GITEA, so the existing token can publish the wiki when it
has write:repository. Update the missing-token message, the credentials and
troubleshooting guides, the README, the tests and the affected English
wiki pages with their Danish and Bahasa Malaysia translations.

Task: MIL-005#8

wiki/Troubleshooting.md

@@ -36,7 +36,8 @@ never starts, or stops before the step) is a **runner** problem.
 | `TOKEN_FOR_GITEA must contain a non-empty GITEA_TOKEN.` | configuration | The JSON form needs a `GITEA_TOKEN` key |
 | `Could not determine the Gitea source repository.` | configuration | The run has no repository name; report as a defect |
 | `Expected at most one GitHub push mirror ... found N` | configuration | Keep one GitHub push mirror |
-| `TOKEN_FOR_GITEA_WIKI is missing or empty.` | configuration | Wiki publishing only: add the secret (see [credentials.md](Credentials)) |
+| `No token for the wiki: set TOKEN_FOR_GITEA_WIKI, or TOKEN_FOR_GITEA.` | configuration | Wiki publishing only: add one of the secrets (see [credentials.md](Credentials)) |
+| `... HTTP 403 ...` while publishing the wiki | permissions | Wiki publishing only: the token needs `write:repository` and write access to this repository |
 | `The wiki is not enabled on <repo>` | configuration | Wiki publishing only: enable the wiki in the repository settings |
 | `The wiki source directory ... has no Markdown pages` | configuration | Wiki publishing only: `wiki/` is empty or missing; nothing was changed |
 | `Could not determine the GitHub owner and repository ...` | configuration | The mirror address must look like `https://github.com/<owner>/<repo>.git` |