The Bootstrap 5 submodule should default to using Bootstrap 5 values

When using the accessible_menu_bootstrap_5 submodule and selecting a Bootstrap 5 variant for accessible menu, the defaults (specifically for open/close/transition classes and transition duration) should be what Bootstrap 5 expects.

Open class: "show" (this is already the default)
Close class: "collapse"
Transition class: "collapsing"
Transition duration: 350