docs: remove 's' from the question

Author: KnupMan

readme.md

@@ -19,7 +19,7 @@ See the table below for other supported regions.
 
 Works well with [aws-lambda-libreoffice npm package](https://github.com/shelfio/aws-lambda-libreoffice)
 
-## What does this layer contains?
+## What does this layer contain?
 
 This layer contains `lo.tar.gz` file which is LibreOfficee v6.1.0.0.alpha (https://github.com/vladgolubev/serverless-libreoffice/releases/tag/v6.1.0.0.alpha0).