fix story re storybook changes

Author: haschek

src/components/Tooltip/Tooltip.stories.tsx

@@ -2,6 +2,7 @@ import React from "react";
 import { loremIpsum } from "react-lorem-ipsum";
 import { OverlaysProvider } from "@blueprintjs/core";
 import { Meta, StoryFn } from "@storybook/react";
+import { fn } from "@storybook/test";
 
 import { Tooltip } from "../../index";
 
@@ -34,6 +35,7 @@ Default.args = {
     children: "hover me",
     content: testContent,
     addIndicator: true,
+    onOpening: fn(),
 };
 
 export const MarkdownSupport = Template.bind({});