fix: benchmarking config template

- Missing [core.tracker_policy] section. Configuration was changed.
- Missing database config. Needed when the default DB folder does not
  exist. With this config storage folder is not needed. WE are not using
DB which required DB for benchmarking.

share/default/config/tracker.udp.benchmarking.toml

@@ -1,6 +1,4 @@
 [metadata]
-app = "torrust-tracker"
-purpose = "configuration"
 schema_version = "2.0.0"
 
 [logging]
@@ -9,8 +7,15 @@ threshold = "error"
 [core]
 listed = false
 private = false
-remove_peerless_torrents = false
 tracker_usage_statistics = false
 
+[core.database]
+driver = "sqlite3"
+path = "./sqlite3.db"
+
+[core.tracker_policy]
+persistent_torrent_completed_stat = false
+remove_peerless_torrents = false
+
 [[udp_trackers]]
 bind_address = "0.0.0.0:6969"