fix sanity test (datacommonsorg#4725)

looks like the class name for topic items got changed in this PR causing
sanity tests to fail:
https://github.com/datacommonsorg/website/pull/4673/files#diff-37059329da755a92aa218821e795bf1cb89ad26682ceb8f6d5dddc84a49bb645L43

server/webdriver/tests/standalone/sanity.py

@@ -145,7 +145,7 @@ def home(self, page: WebPage):
     time.sleep(1)
 
     # topic items
-    topic_items = find_elems(self.driver, By.CLASS_NAME, "topic-item")
+    topic_items = find_elems(self.driver, By.CLASS_NAME, "chip-item")
     if topic_items is None or len(topic_items) == 0:
       self.add_result(fail_result(page, start, "No topic items."))
       return