buddy_list: Add span for search section of header.

This is in preparation for adding a three-dot menu to the header,
which we don't want to be a click/hover target in the way the
search parts are.

web/src/tippyjs.ts

@@ -679,7 +679,7 @@ export function initialize(): void {
     });
 
     tippy.delegate("body", {
-        target: "#userlist-header",
+        target: "#userlist-header-search",
         placement: "top",
         appendTo: () => document.body,
         onShow(instance) {