docs: update Google doodle

Happy birthday~

README.md

@@ -1,8 +1,8 @@
 # Google Hosts
 [![doodle]][doodle-story]
 
-[doodle]: https://www.google.com/logos/doodles/2018/first-day-of-school-2018-5501569482096640-2x.png "开学快乐!"
-[doodle-story]: https://www.google.com/doodles/first-day-of-school-2018
+[doodle]: https://www.google.com/logos/doodles/2018/googles-20th-birthday-6342583134453760-2xa.gif "Google 生日快乐!"
+[doodle-story]: https://www.google.com/doodles/googles-20th-birthday
 
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