lib: remove unnecessary optional chain in diagnostics_channel publish()

ActiveChannel.publish() accessed this._subscribers with optional

chaining (subscribers?.length || 0). This is unnecessary because:

- _subscribers is always initialized to [] by markActive() before any

  ActiveChannel method can be called

- maybeMarkInactive() sets _subscribers back to undefined only after

  switching the prototype back to Channel.prototype, so ActiveChannel

  methods are never reachable with a nullish _subscribers

Use subscribers.length directly.

Signed-off-by: Divyanshu Sharma <divyanshu88999@gmail.com>

Author: DivyanshuX9

lib/diagnostics_channel.js

@@ -300,7 +300,7 @@ class ActiveChannel {
   publish(data) {
     // Normal path, no ALS lookup, plain function call, zero overhead.
     const subscribers = this._subscribers;
-    for (let i = 0; i < (subscribers?.length || 0); i++) {
+    for (let i = 0; i < subscribers.length; i++) {
       try {
         subscribers[i](data, this.name);
       } catch (err) {