[nova][train] Docs: Remove deprecated RetryFilter

The default does not include it.

Nova docs:
RetryFilter - Deprecated since version 20.0.0 (Train)
Since the 17.0.0 (Queens) release, the scheduler has provided
alternate hosts for rescheduling so the scheduler does not need to
be called during a reschedule which makes the RetryFilter useless.

Change-Id: Ic7bfafce40b4025f6768121dec37c1d6f3b4c5fc
(cherry picked from commit a8fa085364)

doc/source/admin/config-sriov.rst

@@ -342,7 +342,7 @@ Configure nova-scheduler (Controller)
    .. code-block:: ini
 
       [filter_scheduler]
-      enabled_filters = RetryFilter, AvailabilityZoneFilter, ComputeFilter, ComputeCapabilitiesFilter, ImagePropertiesFilter, ServerGroupAntiAffinityFilter, ServerGroupAffinityFilter, PciPassthroughFilter
+      enabled_filters = AvailabilityZoneFilter, ComputeFilter, ComputeCapabilitiesFilter, ImagePropertiesFilter, ServerGroupAntiAffinityFilter, ServerGroupAffinityFilter, PciPassthroughFilter
       available_filters = nova.scheduler.filters.all_filters
 
 #. Restart the ``nova-scheduler`` service.