chore: Remove useless play listener when using delayLicenseRequestUntilPlayed as false (#8812)

Author: avelad

lib/drm/drm_engine.js

@@ -577,7 +577,9 @@ shaka.drm.DrmEngine = class {
 
     this.video_ = video;
 
-    this.eventManager_.listenOnce(this.video_, 'play', () => this.onPlay_());
+    if (this.config_.delayLicenseRequestUntilPlayed) {
+      this.eventManager_.listenOnce(this.video_, 'play', () => this.onPlay_());
+    }
     if (this.video_.remote) {
       this.eventManager_.listen(this.video_.remote, 'connect',
           () => this.closeOpenSessions_());