chore(expandable section): add missing aria attributes to examples - #7754

This should be updated to render the aria-controls properly. Right now it's only rendering for detached variants, but we want it regardless of variant as long as an ID is passed.

@mcoker are you opposed to replacing instances of button--IsAriaExpanded in Core handlebars files with just button--IsExpanded? Only 5 instances of IsAriaExpanded in the codebase, and the logic in Button doesn't take that into account when setting the actual aria-expanded attribute (it checks if either IsExpanded or IsAriaExpanded is true, but then only sets aria-expanded based on IsExpanded). Having separate Disabled and AriaDisabled attr is fine since they're distinct things, but there's only an aria-expanded attr so just using IsExpanded is fine.

If you're okay with that, then for this PR we can just update this line to:

button--IsExpanded=(ternary expandable-section--IsExpanded true false)

(since we always want aria-expanded rendered whether true or false for this component), and open a followup for the other files (unless you want to update them here @Mash707, shouldn't take long at all).

@Mash707 ignore this comment for this PR. Coker and I met up to discuss this and I'll put a followup PR to update this across components.