feat(lexicon): marking unstable as @deprecated

Signed-off-by: Maxence Lange <maxence@artificial-owl.com>

Author: ArtificialOwl

lib/unstable/Config/Exceptions/UnknownKeyException.php

@@ -12,7 +12,6 @@
 
 /**
  * @experimental 31.0.0
- * @deprecated
  * @deprecated use \OCP\Config\Exceptions\UnknownKeyException
  * @see \OCP\Config\Exceptions\UnknownKeyException
  */