Remove persistent sessions section from persistence.md

docs/book/persistence.md

@@ -83,33 +83,3 @@ Considering that persistence implementations also _create_ the session instance,
 we recommend that implementations only create instances that implement the
 `SessionIdentifierAwareInterface` going forward in order to make themselves
 async compatible.
-
-## Persistent sessions
-
-- Since 1.2.0.
-
-If your persistence implementation supports persistent sessions — for
-example, by setting an `Expires` or `Max-Age` cookie directive — then you
-can opt to globally set a default session duration, or allow developers to hint
-a desired session duration via the session container using
-`SessionContainerPersistenceInterface::persistSessionFor()`.
-
-Implementations SHOULD honor the value of `SessionContainerPersistenceInterface::getSessionLifetime()`
-when persisting the session data. This could mean either or both of the
-following:
-
-- Ensuring that the session data will not be purged until after the specified
-  TTL value.
-- Setting an `Expires` or `Max-Age` cookie directive.
-
-In each case, the persistence engine should query the `Session` instance for a
-TTL value:
-
-```php
-$ttl = $session instanceof SessionContainerPersistenceInterface
-    ? $session->getSessionLifetime()
-    : $defaultLifetime; // likely 0, to indicate automatic expiry
-```
-
-`getSessionLifetime()` returns an `integer` value indicating the number of
-seconds the session should persist.