refactor(ui/reference_picker): call M.clear_all() instead of direct cache reset

Author: sudo-tee

lua/opencode/ui/reference_picker.lua

@@ -242,7 +242,7 @@ end
 ---Should be called once during plugin initialization
 function M.setup()
   state.store.subscribe('messages', function()
-    cache = {}
+    M.clear_all()
   end)
 end