fix: delay calling vim.ui.select to avoid errors

It occurs an error E5560 when UI to select `y/n` by the user in
validating DB. This delays it until the next tick to avoid errors.

lua/frecency/klass.lua

@@ -99,19 +99,21 @@ function Frecency:validate_database(force)
     remove_entries()
     return
   end
-  vim.ui.select({ "y", "n" }, {
-    prompt = self:message("remove %d entries from database?", #unlinked),
-    ---@param item "y"|"n"
-    ---@return string
-    format_item = function(item)
-      return item == "y" and "Yes. Remove them." or "No. Do nothing."
-    end,
-  }, function(item)
-    if item == "y" then
-      remove_entries()
-    else
-      self:notify "validation aborted"
-    end
+  vim.schedule(function()
+    vim.ui.select({ "y", "n" }, {
+      prompt = self:message("remove %d entries from database?", #unlinked),
+      ---@param item "y"|"n"
+      ---@return string
+      format_item = function(item)
+        return item == "y" and "Yes. Remove them." or "No. Do nothing."
+      end,
+    }, function(item)
+      if item == "y" then
+        remove_entries()
+      else
+        self:notify "validation aborted"
+      end
+    end)
   end)
 end