Update UPGRADE-2.16.md

Co-authored-by: Jeremy Mikola <jmikola@gmail.com>

Author: GromNaN

UPGRADE-2.16.md

@@ -1,8 +1,6 @@
 # UPGRADE FROM 2.15 to 2.16
 
-## Package `doctrine/cache`
-
-The package `doctrine/cache` is no longer required.
+## Package `doctrine/cache` no longer required
 
 If you use `Doctrine\ODM\MongoDB\Configuration::getMetadataCacheImpl()`,
 then you need to require `doctrine/cache` explicitly in `composer.json`;