chore: bump keystone-keycloak-backend to 0.1.8 (#967)

diff --git a/images/keystone/Earthfile b/images/keystone/Earthfile
index 580ef5d..014401a 100644
--- a/images/keystone/Earthfile
+++ b/images/keystone/Earthfile
@@ -10,7 +10,7 @@
     --PROJECT=${PROJECT} \
     --PROJECT_REF=${PROJECT_REF} \
     --EXTRAS "[ldap]" \
-    --PIP_PACKAGES "keystone-keycloak-backend==0.1.6"
+    --PIP_PACKAGES "keystone-keycloak-backend==0.1.8"
 
 image:
   FROM ../openstack-service+image --RELEASE ${RELEASE} --PROJECT ${PROJECT}