Add update schedule note to README

Author: lramosvea

README.md

@@ -149,6 +149,7 @@ try {
 ## Update Schedule
 
 The Microsoft Graph PHP SDK is scheduled to be updated during the week of the second and fourth Tuesday of each month.
+
 ## Upgrading
 
 For detailed information on breaking changes, bug fixes and new functionality introduced during major upgrades, check out our [Upgrade Guide](UPGRADING.md)