Eliminate useless unordered_set

I don't know what this set was originally meant to be doing, but it
currently does nothing (except adding overhead).

The comment says it "owns" the instances but that isn't really true; the
instances effectively already manage themselves as they pass the pointer
through the communications between proxy and workers.

oxenmq/jobs.cpp

@@ -5,7 +5,6 @@
 namespace oxenmq {
 
 void OxenMQ::proxy_batch(detail::Batch* batch) {
-    batches.insert(batch);
     const auto [jobs, tagged_threads] = batch->size();
     OMQ_TRACE("proxy queuing batch job with ", jobs, " jobs", tagged_threads ? " (job uses tagged thread(s))" : "");
     if (!tagged_threads) {
@@ -37,7 +36,6 @@ void OxenMQ::job(std::function<void()> f, std::optional<TaggedThreadID> thread)
 void OxenMQ::proxy_schedule_reply_job(std::function<void()> f) {
     auto* j = new Job(std::move(f));
     reply_jobs.emplace_back(static_cast<detail::Batch*>(j), 0);
-    batches.insert(j);
     proxy_skip_one_poll = true;
 }
 
@@ -113,7 +111,6 @@ void OxenMQ::_queue_timer_job(int timer_id) {
     } else {
         b = new Job(func, thread);
     }
-    batches.insert(b);
     OMQ_TRACE("b: ", b->size().first, ", ", b->size().second, "; thread = ", thread);
     assert(b->size() == std::make_pair(size_t{1}, thread > 0));
     auto& queue = thread > 0

oxenmq/oxenmq.h

@@ -576,8 +576,6 @@ private:
     /// weaker (i.e. it cannot reconnect to the SN if the connection is no longer open).
     void proxy_reply(oxenc::bt_dict_consumer data);
 
-    /// Currently active batch/reply jobs; this is the container that owns the Batch instances
-    std::unordered_set<detail::Batch*> batches;
     /// Individual batch jobs waiting to run; .second is the 0-n batch number or -1 for the
     /// completion job
     using batch_job = std::pair<detail::Batch*, int>;

oxenmq/worker.cpp

@@ -247,7 +247,6 @@ void OxenMQ::proxy_worker_message(std::vector<zmq::message_t>& parts) {
             }
 
             if (clear_job) {
-                batches.erase(batch);
                 delete batch;
                 run.to_run = static_cast<detail::Batch*>(nullptr);
             }