Improve wording a bit

docs/configuring-playbook-s3.md

@@ -1,4 +1,4 @@
-# Amazon S3 configuration (optional)
+# Storing Matrix media files on Amazon S3 (optional)
 
 By default, this playbook configures your server to store Matrix Synapse's content repository (`media_store`) files on the local filesystem.
 If that's alright, you can skip this.

docs/configuring-playbook.md

@@ -23,7 +23,7 @@ When you're done with all the configuration you'd like to do, continue with [Ins
 
 ## Other configuration options
 
-- [Amazon S3 configuration](configuring-playbook-s3.md) (optional)
+- [Storing Matrix media files on Amazon S3](configuring-playbook-s3.md) (optional)
 
 - [Using an external PostgreSQL server](configuring-playbook-external-postgres.md) (optional)