Fix typo

Co-authored-by: Vinay Vyas <[email protected]>

Author: PierrickVoulet

solutions/ooo-assistant/README.md

@@ -1,6 +1,6 @@
 # Build a Google Workspace add-on extending all UIs
 
-**Warning:** This sample build a Chat app as a Google Workspace add-on. It's only available in the [Developer Preview Program](https://developers.google.com/workspace/preview).
+**Warning:** This sample builds a Chat app as a Google Workspace add-on. It's only available in the [Developer Preview Program](https://developers.google.com/workspace/preview).
 
 The add-on extends the following Google Workspace UIs: Chat, Calendar, Gmail, Drive, Docs, Sheets, and Slides.