Lock - replace getExpiringDate by getRemainingLifetime

As the method `getExpiringDate` doesn't exist, replace it by `getRemainingLifetime` which returns the remaining time to live in seconds

Author: ybenhssaien

components/lock.rst

@@ -203,8 +203,8 @@ to reset the TTL to its original value::
         $lock->refresh(600);
 
 This component also provides two useful methods related to expiring locks:
-``getExpiringDate()`` (which returns ``null`` or a ``\DateTimeImmutable``
-object) and ``isExpired()`` (which returns a boolean).
+``getRemainingLifetime()`` (which returns ``null`` or a ``float``
+as seconds) and ``isExpired()`` (which returns a boolean).
 
 Shared Locks
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