batchlog_manager: Remove start() method

It's now a no-op, can be dropped.

Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>

db/batchlog_manager.cc

@@ -111,10 +111,6 @@ future<> db::batchlog_manager::batchlog_replay_loop() {
     }
 }
 
-future<> db::batchlog_manager::start() {
-    return make_ready_future<>();
-}
-
 future<> db::batchlog_manager::drain() {
     if (_stop.abort_requested()) {
         co_return;

db/batchlog_manager.hh

@@ -75,7 +75,6 @@ public:
     // shard qp (which is what you feed here).
     batchlog_manager(cql3::query_processor&, db::system_keyspace& sys_ks, batchlog_manager_config config);
 
-    future<> start();
     // abort the replay loop and return its future.
     future<> drain();
     future<> stop();

main.cc

@@ -1718,7 +1718,6 @@ To start the scylla server proper, simply invoke as: scylla server (or just scyl
             auto stop_batchlog_manager = defer_verbose_shutdown("batchlog manager", [&bm] {
                 bm.stop().get();
             });
-            bm.invoke_on_all(&db::batchlog_manager::start).get();
 
             supervisor::notify("starting load meter");
             load_meter.init(db, gossiper.local()).get();