fix #3630

Closes #3630

Merge request studip/studip!2515

resources/assets/stylesheets/scss/courseware.scss

@@ -22,6 +22,7 @@
 
 
 @import './courseware/layouts/call-to-action.scss';
+@import './courseware/layouts/collapsible.scss';
 @import './courseware/layouts/companion.scss';
 @import './courseware/layouts/import-zip.scss';
 @import './courseware/layouts/input-file.scss';
@@ -30,4 +31,4 @@
 @import './courseware/layouts/tabs.scss';
 @import './courseware/layouts/talk-bubble.scss';
 @import './courseware/layouts/tile.scss';
-@import './courseware/layouts/tree.scss';
\ No newline at end of file
+@import './courseware/layouts/tree.scss';