gluon-announce: Remove now unused collect.lua

The file promotes the probably unnecessary re-execution of the announce
scripts. Instead, gluon-announced should be queried using

    gluon-neighbour-info -d ::1 -p 1001 -t0 -r nodeinfo

if both gluon-announced and gluon-neighbour-info are present. But to not
depend on any of those, no script for this one-liner is provided.

package/gluon-announce/files/lib/gluon/announce/collect.lua

-#!/usr/bin/lua
-
-local announce = require 'gluon.announce'
-local json = require 'luci.jsonc'
-
-local announce_dir = '/lib/gluon/announce/' .. arg[1] .. '.d'
-
-print(json.stringify(announce.collect_dir(announce_dir)))