docs(component): Replace VolumeMenuButton with VolumePanel in component tree (#4267)

Video.js 6 has switch to using the VolumePanel instead of the VolumeMenuButton.

Fixes #4266

docs/guides/components.md

@@ -292,7 +292,7 @@ Player
 ├── BigPlayButton
 ├─┬ ControlBar
 │ ├── PlayToggle
-│ ├── VolumeMenuButton
+│ ├── VolumePanel
 │ ├── CurrentTimeDisplay (hidden by default)
 │ ├── TimeDivider (hidden by default)
 │ ├── DurationDisplay (hidden by default)