chore: move JSON license metadata to sidecar

Signed-off-by: Vitor Mattos <vitor@php.rio>

Author: vitormattos

upstream/sources.json

@@ -1,5 +1,3 @@
 {
-  "SPDX-FileCopyrightText": "2026 LibreCode coop and contributors",
-  "SPDX-License-Identifier": "AGPL-3.0-or-later",
   "sources": []
 }