Bluetooth: GATT: Fix not clearing out of sync flag

When the database changes and a client becomes change unware it should
also clear the out of sync flag as the following request should return
an error:

Core Spec 5.1 | Vol 3, Part G, 2.5.2.1 Robust Caching:

  'The error response is sent only once after the client becomes
  change-unaware, unless the client disconnects or the database changes
  again before the client becomes change-aware in which case the error
  response shall be sent again.'

Fixes: #18183

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>