remove ebtables fix env var from wallaby stable job

Per review feedback on
https://review.opendev.org/c/openstack/ironic-tempest-plugin/+/798143
it is believe the setting is no longer required for Wallaby branches.

Change-Id: I9face242ac4501a37a36534dd05eba66466fcccc
diff --git a/zuul.d/stable-jobs.yaml b/zuul.d/stable-jobs.yaml
index 7e0fb52..6e96c34 100644
--- a/zuul.d/stable-jobs.yaml
+++ b/zuul.d/stable-jobs.yaml
@@ -93,10 +93,6 @@
     name: ironic-inspector-tempest-wallaby
     parent: ironic-inspector-tempest
     override-checkout: stable/wallaby
-    vars:
-      devstack_localrc:
-        FIXED_NETWORK_SIZE: 4096
-        EBTABLES_RACE_FIX: True
 
 - job:
     name: ironic-inspector-tempest-victoria
@@ -105,7 +101,6 @@
     vars:
       devstack_localrc:
         FIXED_NETWORK_SIZE: 4096
-        EBTABLES_RACE_FIX: True
 
 - job:
     name: ironic-inspector-tempest-ussuri