Two collapse elements get same ID

[hupf]

Using the Collapsed Panel component as described in https://swiss.github.io/styleguide/en/content-containers.html#02-content-containers-03-collapsible-panel, I found out that from time to time two collapse elements get the same id. This produces non-valid HTML and caused our axe-core test to be flaky. It is due to the uniqueId Implementation of the bootstrap-accessibility-plugin and should be fixed in the used fork of this library.