Nested collapsible fieldsets can't be expanded

[aanckar]

When nesting an object field with collapsible fieldsets inside an array field, the collapsed fieldsets can't be expanded (clicking doesn't do anything). Example schema here.

This issue appears eg. when using field level translations following the recommended approach inside an array field.

Steps to reproduce:

1. Use example repo (https://github.com/aanckar/sanity-studio-v3-test)
2. Launch studio, create a page
3. Add an item to the blocks field
4. Attempt to expand the translations fieldset

[wernerglinka]

It seems that collapsible doesn't work, regardless what the initial state is.