Remove modal header for smart picker dialogs

Hide the empty modal header which prevents from accessing the close button
Cannot use display:none because there's a `display: flex !important` in the
Ncmodal component which would override it. This works because the
`.modal-header` element has `position: absolute`.
TODO: Add prop to NcModal to hide the header

Signed-off-by: Marco Ambrosini <marcoambrosini@proton.me>

Author: marcoambrosini

src/components/NcRichText/NcReferencePicker/NcReferencePickerModal.vue

@@ -186,4 +186,13 @@ export default {
 		}
 	}
 }
+// Hide the empty modal header which prevents from accessing the close button 
+// Cannot use display:none because there's a `display: flex !important` in the
+// Ncmodal component which would override it. This works because the
+// `.modal-header` element has `position: absolute`.
+// TODO: Add prop to NcModal to hide the header
+:deep(.modal-header) {
+	visibility: hidden; 
+}
+
 </style>