nextcloud: pin an image whose PHP matches this Nextcloud version

The pinned digest resolved to a PHP 8.5.10 image; Nextcloud 30 refuses to
run above PHP 8.4. Repinned to the current digest for the nextcloud:30 tag
(matches HAL's own NEXTCLOUD_VERSION), which carries PHP 8.3.28 -- the
same version the data being migrated was actually running under.

modules/nextcloud/module.json

@@ -78,7 +78,7 @@
       "id": "server",
       "type": "container",
       "name": "nextcloud",
-      "image": "nextcloud@sha256:0b8261f6335af6b95264ce893b4d645857638e0fa151b5ba620f25f377318ae1",
+      "image": "nextcloud@sha256:fb966733647ea03f0446b0c22eac9733c8eb616d37b960caca9d4c3010e14a08",
       "env-file": [
         "/var/lib/nextcloud-module/server.env"
       ],