README: drop the dev basic auth credentials

The vitecdev password has been rotated today (htpasswd on the server, new value distributed via the password manager and set as VITEC_API_AUTH on the SSR VPS). Credentials do not belong in the repository; the leaked value is invalid as of now.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -168,7 +168,3 @@ bash fix-asset-perms.sh                                   # fix asset permission
 [GPL‑2.0‑or‑later](LICENSE) — © evomedien.
 
 <div align="center"><sub>VITEC · TYPO3 headless backend + React front end</sub></div>
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