Simplify `this.isActive() && this.webSocket` into `this.isActive()`

in Connection#close. We can do this because `isActive()` can only
return `true` if `this.webSocket` is truthy. (We can't have an active
connection without having instantiated a WebSocket. This is confirmed
in the code: Connection#isActive calls Connection#isState which calls
Connection#getState, which checks if `this.webSocket` is truthy and
returns `null` otherwise.)

actioncable/app/assets/javascripts/action_cable.js

@@ -191,7 +191,7 @@
       if (!allowReconnect) {
         this.monitor.stop();
       }
-      if (this.isActive() && this.webSocket) {
+      if (this.isActive()) {
         return this.webSocket.close();
       }
     };

actioncable/app/javascript/action_cable/connection.js

@@ -44,7 +44,7 @@ class Connection {
 
   close({allowReconnect} = {allowReconnect: true}) {
     if (!allowReconnect) { this.monitor.stop() }
-    if (this.isActive() && this.webSocket) {
+    if (this.isActive()) {
       return this.webSocket.close()
     }
   }