fix(typings): update return type from emit (#3843)

```
(channel ? io.to(channel) : io).emit("stuff", message);
```

would no longer compile.

Related: #3844

Author: solomon23

lib/broadcast-operator.ts

@@ -133,7 +133,7 @@ export class BroadcastOperator<EmitEvents extends EventsMap>
   public emit<Ev extends EventNames<EmitEvents>>(
     ev: Ev,
     ...args: EventParams<EmitEvents, Ev>
-  ): true {
+  ): boolean {
     if (RESERVED_EVENTS.has(ev)) {
       throw new Error(`"${ev}" is a reserved event name`);
     }
@@ -276,7 +276,7 @@ export class RemoteSocket<EmitEvents extends EventsMap>
   public emit<Ev extends EventNames<EmitEvents>>(
     ev: Ev,
     ...args: EventParams<EmitEvents, Ev>
-  ): true {
+  ): boolean {
     return this.operator.emit(ev, ...args);
   }
 

lib/namespace.ts

@@ -229,7 +229,7 @@ export class Namespace<
   public emit<Ev extends EventNames<EmitEvents>>(
     ev: Ev,
     ...args: EventParams<EmitEvents, Ev>
-  ): true {
+  ): boolean {
     return new BroadcastOperator<EmitEvents>(this.adapter).emit(ev, ...args);
   }
 

lib/parent-namespace.ts

@@ -35,7 +35,7 @@ export class ParentNamespace<
   public emit<Ev extends EventNames<EmitEvents>>(
     ev: Ev,
     ...args: EventParams<EmitEvents, Ev>
-  ): true {
+  ): boolean {
     this.children.forEach((nsp) => {
       nsp.emit(ev, ...args);
     });