client/web: remove DebugMode from GET /api/data

No longer using this! Readonly state fully managed via auth endpoint.
Also getting rid of old Legacy server mode.

A #cleanup

Signed-off-by: Sonia Appasamy <sonia@tailscale.com>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f