[nova][train] Remove deprecated RetryFilter

Affects config with Blazar and fake Nova only.
The default does not include it.

Upstream 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: I26bf45997005124e9166b5bf1d44cb276624430b

ansible/roles/nova/templates/nova.conf.j2

@@ -33,10 +33,10 @@ transport_url = {{ rpc_transport_url }}
 {% if enable_blazar | bool %}
 available_filters = nova.scheduler.filters.all_filters
 available_filters = blazarnova.scheduler.filters.blazar_filter.BlazarFilter
-enabled_filters = RetryFilter,AvailabilityZoneFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter,BlazarFilter
+enabled_filters = AvailabilityZoneFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter,BlazarFilter
 {% endif %}
 {% if enable_nova_fake | bool %}
-enabled_filters = RetryFilter,AvailabilityZoneFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter
+enabled_filters = AvailabilityZoneFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter
 {% endif %}
 {% if enable_cells | bool %}
 # When in superconductor mode, nova-compute can't send instance

releasenotes/notes/nova-remove-deprecated-retryfilter-2e1c0667148c3c99.yaml

+---
+other:
+  - |
+    The upstream-deprecated Nova RetryFilter has been removed from
+    Blazar-enabled and fake Nova config. It has no effect since
+    Queens.