Remove reliable websockets configuration (#19040)

The feature is stable enough to be removed
as a config knob.

For backwards compatiblity with older mobile
clients, we keep sending the config param
as true for client config requests.

https://community-daily.mattermost.com/boards/workspace/zyoahc9uapdn3xdptac6jb69ic/285b80a3-257d-41f6-8cf4-ed80ca9d92e5/495cdb4d-c13a-4992-8eb9-80cfee2819a4/7m95frqbk9o8zxin6xo9c7iusoh

```release-note
NONE
```

app/web_conn.go

@@ -181,7 +181,7 @@ func (a *App) NewWebConn(cfg *WebConnConfig) *WebConn {
 		cfg.activeQueue = make(chan model.WebSocketMessage, sendQueueSize)
 	}
 
-	if cfg.deadQueue == nil && *a.ch.srv.Config().ServiceSettings.EnableReliableWebSockets {
+	if cfg.deadQueue == nil {
 		cfg.deadQueue = make([]*model.WebSocketEvent, deadQueueSize)
 	}
 
@@ -375,7 +375,7 @@ func (wc *WebConn) writePump() {
 		wc.WebSocket.Close()
 	}()
 
-	if *wc.App.Srv().Config().ServiceSettings.EnableReliableWebSockets && wc.Sequence != 0 {
+	if wc.Sequence != 0 {
 		if ok, index := wc.isInDeadQueue(wc.Sequence); ok {
 			if err := wc.drainDeadQueue(index); err != nil {
 				wc.logSocketErr("websocket.drainDeadQueue", err)
@@ -472,8 +472,7 @@ func (wc *WebConn) writePump() {
 				mlog.Warn("websocket.full", logData...)
 			}
 
-			if *wc.App.Srv().Config().ServiceSettings.EnableReliableWebSockets &&
-				evtOk {
+			if evtOk {
 				wc.addToDeadQueue(evt)
 			}
 

app/web_conn_test.go

@@ -155,8 +155,6 @@ func TestWebConnAddDeadQueue(t *testing.T) {
 	th := Setup(t)
 	defer th.TearDown()
 
-	th.App.UpdateConfig(func(cfg *model.Config) { *cfg.ServiceSettings.EnableReliableWebSockets = true })
-
 	wc := th.App.NewWebConn(&WebConnConfig{
 		WebSocket: &websocket.Conn{},
 	})
@@ -186,10 +184,6 @@ func TestWebConnIsInDeadQueue(t *testing.T) {
 	th := Setup(t)
 	defer th.TearDown()
 
-	th.App.UpdateConfig(func(cfg *model.Config) {
-		*cfg.ServiceSettings.EnableReliableWebSockets = true
-	})
-
 	wc := th.App.NewWebConn(&WebConnConfig{
 		WebSocket: &websocket.Conn{},
 	})
@@ -251,10 +245,6 @@ func TestWebConnDrainDeadQueue(t *testing.T) {
 	th := Setup(t)
 	defer th.TearDown()
 
-	th.App.UpdateConfig(func(cfg *model.Config) {
-		*cfg.ServiceSettings.EnableReliableWebSockets = true
-	})
-
 	var dialConn = func(t *testing.T, a *App, addr net.Addr) *WebConn {
 		d := websocket.Dialer{}
 		c, _, err := d.Dial("ws://"+addr.String()+"/ws", nil)

app/web_hub.go

@@ -465,11 +465,7 @@ func (h *Hub) Start() {
 			case webConn := <-h.unregister:
 				// If already removed (via queue full), then removing again becomes a noop.
 				// But if not removed, mark inactive.
-				if *h.srv.Config().ServiceSettings.EnableReliableWebSockets {
-					webConn.active = false
-				} else {
-					connIndex.Remove(webConn)
-				}
+				webConn.active = false
 
 				atomic.StoreInt64(&h.connectionCount, int64(connIndex.AllActive()))