[Glitch] Rewrite actions/modal and reducers/modal with typescript

Port 38c6216082 to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/features/ui/components/header.jsx

@@ -27,7 +27,7 @@ const mapStateToProps = (state) => ({
 
 const mapDispatchToProps = (dispatch) => ({
   openClosedRegistrationsModal() {
-    dispatch(openModal('CLOSED_REGISTRATIONS'));
+    dispatch(openModal({ modalType: 'CLOSED_REGISTRATIONS' }));
   },
 });